JP7229669B2 - SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE - Google Patents

Description

One embodiment of the present invention relates to a semiconductor device and a method for manufacturing the semiconductor device. Alternatively, one aspect of the present invention relates to semiconductor wafers, modules, and electronic devices.

Note that a semiconductor device in this specification and the like refers to all devices that can function by utilizing semiconductor characteristics. A semiconductor element such as a transistor, a semiconductor circuit, an arithmetic device, and a memory device are examples of semiconductor devices. Display devices (liquid crystal display devices, light-emitting display devices, etc.), projection devices, lighting devices, electro-optic devices, power storage devices, storage devices, semiconductor circuits, imaging devices, electronic devices, and the like can be said to have semiconductor devices in some cases. .

Note that one embodiment of the present invention is not limited to the above technical field. One embodiment of the invention disclosed in this specification and the like relates to a product, a method, or a manufacturing method. Alternatively, one aspect of the invention relates to a process, machine, manufacture, or composition of matter.

Silicon-based semiconductor materials are widely known as semiconductor thin films applicable to transistors, but oxide semiconductors are attracting attention as other materials. As oxide semiconductors, for example, not only single-component metal oxides such as indium oxide and zinc oxide, but also multi-component metal oxides are known. In--Ga--Zn oxides (hereinafter also referred to as IGZO) have been extensively studied among multicomponent metal oxides.

Research on IGZO has found a CAAC (c-axis aligned crystalline) structure and an nc (nanocrystalline) structure, which are neither single crystal nor amorphous, in oxide semiconductors (see Non-Patent Documents 1 to 3). .). Non-Patent Document 1 and Non-Patent Document 2 also disclose a technique for manufacturing a transistor using an oxide semiconductor having a CAAC structure. Furthermore, Non-Patent Document 4 and Non-Patent Document 5 show that even an oxide semiconductor having a crystallinity lower than that of the CAAC structure and the nc structure has minute crystals.

Furthermore, a transistor using IGZO as an active layer has an extremely low off-state current (see Non-Patent Document 6), and LSIs and displays utilizing this characteristic have been reported (see Non-Patent Document 7 and Non-Patent Document 8). .).

S. Yamazaki et al. , "SID Symposium Digest of Technical Papers", 2012, volume 43, issue 1, p. 183-186 S. Yamazaki et al. , "Japanese Journal of Applied Physics", 2014, volume 53, Number 4S, p. 04ED18-1-04ED18-10 S. Ito et al. , "The Proceedings of AM-FPD'13 Digest of Technical Papers", 2013, p. 151-154 S. Yamazaki et al. , "ECS Journal of Solid State Science and Technology", 2014, volume 3, issue 9, p. Q3012-Q3022 S. Yamazaki, "ECS Transactions", 2014, volume 64, issue 10, p. 155-164 K. Kato et al. , "Japanese Journal of Applied Physics", 2012, volume 51, p. 021201-1-021201-7 S. Matsuda et al. , "2015 Symposium on VLSI Technology Digest of Technical Papers", 2015, p. T216-T217 S. Amano et al. , "SID Symposium Digest of Technical Papers", 2010, volume 41, issue 1, p. 626-629

An object of one embodiment of the present invention is to provide a semiconductor device with high on-state current. Another object of one embodiment of the present invention is to provide a semiconductor device with high frequency characteristics. Another object of one embodiment of the present invention is to provide a highly reliable semiconductor device. Another object of one embodiment of the present invention is to provide a semiconductor device that can be miniaturized or highly integrated. Another object of one embodiment of the present invention is to provide a semiconductor device with favorable electrical characteristics. Another object of one embodiment of the present invention is to provide a highly productive semiconductor device.

An object of one embodiment of the present invention is to provide a semiconductor device capable of holding data for a long time. An object of one embodiment of the present invention is to provide a semiconductor device in which data can be written at high speed. An object of one embodiment of the present invention is to provide a semiconductor device with a high degree of freedom in design. An object of one embodiment of the present invention is to provide a semiconductor device that can consume less power. An object of one embodiment of the present invention is to provide a novel semiconductor device.

The description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Problems other than these are self-evident from the descriptions of the specification, drawings, claims, etc., and it is possible to extract problems other than these from the descriptions of the specification, drawings, claims, etc. is.

One aspect of the invention includes a first insulator, an oxide over the first insulator, a first conductor and a second conductor over the oxide, and a second insulator over the oxide. a body, a third conductor overlying the second insulator and overlapping the oxide, the first insulator, side surfaces of the oxide, side surfaces of the first conductor, and top surface of the first conductor. , a third insulator in contact with the side surface of the second conductor, the top surface of the second conductor, and the side surface of the second insulator, and the third conductor, the second insulator, and the third insulator. a fourth insulator on the insulator of, the fourth insulator in contact with the top surface of each of the third conductor, the second insulator, and the third insulator; It is a semiconductor device.

One embodiment of the present invention includes a first insulator, an oxide over the first insulator, a first conductor and a second conductor over the oxide, and a second conductor over the oxide. and a third conductor overlying the second insulator and overlapping the oxide, the oxide being the first oxide and the second conductor over the first oxide. a first insulator, a side of the first oxide, a side of the second oxide, and a side of the first conductor, comprising an oxide and a third oxide on the second oxide; , a top surface of the first conductor, a side surface of the second conductor, a top surface of the second conductor, and a side surface of the third oxide; a second insulator, a third oxide, and a fourth insulator over the third insulator, the fourth insulator comprising the third conductor, the second insulator, and the fourth insulator; 3 oxide and a third insulator.

Further, it is preferable that the third insulator and the fourth insulator each have a lower permeability to one or both of oxygen and hydrogen than the first insulator.

Further, it is preferable that the third insulator and the fourth insulator each have a lower permeability to one or both of oxygen and hydrogen than the second insulator.

Also, the third insulator and the fourth insulator may each be an oxide containing one or both of aluminum and hafnium.

Also, the third insulator and the fourth insulator may each be aluminum oxide.

Also, the oxide preferably contains In, an element M (M is Al, Ga, Y, or Sn), and Zn.

In addition, the oxide has a first region that does not overlap with the first conductor and the second conductor and a second region that overlaps with the first conductor and the second conductor; One region may have a thinner portion than the second region.

Further, the first conductor and the second conductor respectively contain a first element and a second element, the first element having higher oxidation resistance than the second element, and the second element may have a smaller work function than the first element.

The first element is one or more of Ru, Rh, Pd, Os, Ir, and Pt, and the second element is Al, Si, Ti, Hf, Zr, Mn, In, Any one or more of Ga, Bi, Ta, Nb, Zn, Sn, Cu, Cr, W, Mo, Ge, Ni, Sc, Y, and Ce may be used.

In one embodiment of the present invention, a first insulator is formed over a substrate, an oxide film and a first conductive film are sequentially formed over the first insulator, and the oxide film and the first conductive film are formed. processing the conductive film to form an oxide and a conductive layer; forming a dummy gate film covering the oxide and the conductive layer; processing the dummy gate film to form a dummy gate layer; forming a first insulating film covering the insulator, oxide, conductor layer and dummy gate layer; forming a second insulating film on the first insulating film; forming a first insulating film; by performing CMP treatment, removing part of the first insulating film and the second insulating film until part of the dummy gate layer is exposed, and etching part of the conductor layer and the dummy gate layer. Thus, a first conductor and a second conductor are formed, an oxide is exposed, heat treatment is performed, a third insulating film is formed, a second conductive film is formed, and a second conductive film is formed. removing the third insulating film and the second conductive film until a part of the second insulating film is exposed by performing a CMP treatment to form a third insulator and a third conductor; In the method for manufacturing a semiconductor device, a fourth insulating film is formed to cover the second insulating film, the third insulator, and the third conductor.

According to one embodiment of the present invention, a semiconductor device with high on-state current can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with high frequency characteristics can be provided. Alternatively, according to one embodiment of the present invention, a highly reliable semiconductor device can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device that can be miniaturized or highly integrated can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with favorable electrical characteristics can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with high productivity can be provided.

Alternatively, a semiconductor device capable of holding data for a long time can be provided. Alternatively, a semiconductor device with high data writing speed can be provided. Alternatively, a semiconductor device with a high degree of freedom in design can be provided. Alternatively, a semiconductor device with low power consumption can be provided. Alternatively, a novel semiconductor device can be provided.

Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not need to have all of these effects. Effects other than these are self-evident from the descriptions of the specification, drawings, claims, etc., and it is possible to extract effects other than these from the descriptions of the specification, drawings, claims, etc. is.

1A and 1B are a top view and a cross-sectional view of a semiconductor device according to one embodiment of the present invention; 1A and 1B are cross-sectional views of a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and a cross-sectional view of a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are a top view and cross-sectional views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention; 1A and 1B are cross-sectional views each illustrating a structure of a memory device according to one embodiment of the present invention; 1A and 1B are cross-sectional views each illustrating a structure of a memory device according to one embodiment of the present invention; 1 is a block diagram illustrating a configuration example of a storage device according to one embodiment of the present invention; FIG. 1 is a circuit diagram illustrating a configuration example of a memory device according to one embodiment of the present invention; FIG. 1A and 1B are schematic diagrams of a semiconductor device according to one embodiment of the present invention; 1A and 1B are schematic diagrams of a memory device according to one embodiment of the present invention; 1A and 1B illustrate electronic devices according to one embodiment of the present invention;

Hereinafter, embodiments will be described with reference to the drawings. However, those skilled in the art will readily appreciate that the embodiments can be embodied in many different forms and that various changes in form and detail can be made without departing from the spirit and scope thereof. be. Therefore, the present invention should not be construed as being limited to the description of the following embodiments.

Also, in the drawings, sizes, layer thicknesses, or regions may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale. The drawings schematically show ideal examples, and are not limited to the shapes or values shown in the drawings. For example, in an actual manufacturing process, layers, resist masks, and the like may be unintentionally reduced due to processing such as etching, but are sometimes omitted for ease of understanding. In addition, in the drawings, the same reference numerals may be used in common for the same parts or parts having similar functions, and repeated description thereof may be omitted. Moreover, when referring to similar functions, the hatch patterns may be the same and no particular reference numerals may be attached.

In particular, in top views (also referred to as “plan views”) and perspective views, description of some components may be omitted in order to facilitate understanding of the invention. Also, description of some hidden lines may be omitted.

In this specification and the like, the ordinal numbers such as first and second are used for convenience and do not indicate the order of steps or the order of stacking. Therefore, for example, "first" can be appropriately replaced with "second" or "third". Also, the ordinal numbers described in this specification and the like may not match the ordinal numbers used to specify one aspect of the present invention.

In this specification and the like, terms such as “above” and “below” are used for convenience in order to describe the positional relationship between configurations with reference to the drawings. In addition, the positional relationship between the configurations changes appropriately according to the direction in which each configuration is drawn. Therefore, it is not limited to the words and phrases described in the specification, and can be appropriately rephrased according to the situation.

For example, in this specification and the like, when X and Y are directly connected and when it is explicitly stated that X and Y are connected, X and Y are electrically The present specification and the like disclose the case where X and Y are functionally connected and the case where X and Y are functionally connected. Therefore, it is assumed that the connection relationships other than the connection relationships shown in the drawings or the text are not limited to the predetermined connection relationships, for example, the connection relationships shown in the drawings or the text.

Here, X and Y are objects (for example, devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

Also, the functions of the source and the drain may be interchanged when using transistors of different polarities or when the direction of current changes in circuit operation. Therefore, in this specification and the like, the terms "source" and "drain" can be used interchangeably in some cases.

Note that in this specification and the like, depending on the structure of a transistor, the channel width in a region where a channel is actually formed (hereinafter also referred to as an "effective channel width") and the channel width shown in a top view of the transistor. (hereinafter also referred to as “apparent channel width”). For example, when the gate electrode covers the side surface of the semiconductor, the effective channel width becomes larger than the apparent channel width, and its influence cannot be ignored. For example, in a fine transistor in which a gate electrode covers the side surface of a semiconductor, the proportion of the channel formation region formed on the side surface of the semiconductor may be large. In that case, the effective channel width is larger than the apparent channel width.

In such a case, it may be difficult to estimate the effective channel width by actual measurement. For example, in order to estimate the effective channel width from design values, it is necessary to assume that the shape of the semiconductor is known. Therefore, it is difficult to accurately measure the effective channel width if the shape of the semiconductor is not accurately known.

In this specification, simply describing the channel width may refer to the apparent channel width. Alternatively, in this specification, simply referring to the channel width may refer to the effective channel width. The values of the channel length, channel width, effective channel width, apparent channel width, etc. can be determined by analyzing a cross-sectional TEM image or the like.

Note that impurities in a semiconductor refer to, for example, substances other than the main components that constitute the semiconductor. For example, an element whose concentration is less than 0.1 atomic percent can be said to be an impurity. When impurities are contained, for example, the DOS (Density of States) of the semiconductor may increase, the crystallinity may decrease, and the like. When the semiconductor is an oxide semiconductor, impurities that change the characteristics of the semiconductor include, for example, group 1 elements, group 2 elements, group 13 elements, group 14 elements, group 15 elements, and oxide semiconductors. There are transition metals other than the main component of , such as hydrogen, lithium, sodium, silicon, boron, phosphorus, carbon, and nitrogen. In the case of an oxide semiconductor, water may also function as an impurity. In the case of an oxide semiconductor, for example, oxygen vacancies may be formed due to contamination by impurities. When the semiconductor is silicon, impurities that change the characteristics of the semiconductor include, for example, group 1 elements, group 2 elements, group 13 elements, and group 15 elements excluding oxygen and hydrogen.

Note that in this specification and the like, silicon oxynitride contains more oxygen than nitrogen as its composition. Silicon nitride oxide contains more nitrogen than oxygen in its composition.

In this specification and the like, the term “insulator” can be replaced with an insulating film or an insulating layer. Also, the term “conductor” can be replaced with a conductive film or a conductive layer. Also, the term "semiconductor" can be interchanged with a semiconductor film or a semiconductor layer.

In this specification and the like, "parallel" means a state in which two straight lines are arranged at an angle of -10 degrees or more and 10 degrees or less. Therefore, the case of -5 degrees or more and 5 degrees or less is also included. Also, "substantially parallel" means a state in which two straight lines are arranged at an angle of -30 degrees or more and 30 degrees or less. "Perpendicular" means that two straight lines are arranged at an angle of 80 degrees or more and 100 degrees or less. Therefore, the case of 85 degrees or more and 95 degrees or less is also included. In addition, "substantially perpendicular" means a state in which two straight lines are arranged at an angle of 60 degrees or more and 120 degrees or less.

Note that in this specification, a barrier film is a film that has a function of suppressing permeation of impurities such as water and hydrogen, and oxygen. I may call

In this specification and the like, a metal oxide is a metal oxide in broad terms. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as oxide semiconductors or simply OSs), and the like. For example, when a metal oxide is used for a semiconductor layer of a transistor, the metal oxide is sometimes called an oxide semiconductor. In other words, an OS FET or an OS transistor can also be referred to as a transistor including an oxide or an oxide semiconductor.

In this specification and the like, the term “normally off” means that a current per 1 μm of channel width flowing through a transistor when no potential is applied to the gate or when a ground potential is applied to the gate is 1×10 ⁻²⁰ at room temperature. A or less, 1×10 ⁻¹⁸ A or less at 85° C., or 1×10 ⁻¹⁶ A or less at 125° C.

(Embodiment 1)
An example of a semiconductor device including the transistor 200 according to one embodiment of the present invention is described below.

<Structure example of semiconductor device>
1A, 1B, and 1C are a top view and a cross-sectional view of a transistor 200 and its periphery according to one embodiment of the present invention.

FIG. 1A is a top view of a semiconductor device including a transistor 200. FIG. 1B and 1C are cross-sectional views of the semiconductor device. Here, FIG. 1B is a cross-sectional view of the portion indicated by the dashed-dotted line A1-A2 in FIG. 1A, and is also a cross-sectional view of the transistor 200 in the channel length direction. FIG. 1C is a cross-sectional view of the portion indicated by the dashed-dotted line A3-A4 in FIG. 1A, and is also a cross-sectional view of the transistor 200 in the channel width direction. Note that in the top view of FIG. 1A, some elements are omitted for clarity.

A semiconductor device of one embodiment of the present invention includes a transistor 200 and insulators 210, 212, 274, 280, and 281 functioning as interlayer films. It also includes a conductor 203 that is electrically connected to the transistor 200 and functions as a wiring, and a conductor 240 (a conductor 240a and a conductor 240b) that functions as a plug. Note that insulators 241 (insulators 241a and 241b) are provided in contact with side surfaces of conductors 240 functioning as plugs.

Note that the conductor 203 is formed so as to be embedded in the insulator 212 . Here, the height of the upper surface of the conductor 203 and the height of the upper surface of the insulator 212 can be made approximately the same. Note that the conductor 203 has a single layer structure, but the present invention is not limited to this. For example, the conductor 203 may have two layers of a first conductor and a second conductor, or may have a multilayer structure of two or more layers. In addition, when the structure has a laminated structure, an ordinal number may be given in order of formation for distinction.

In addition, the insulator 241 is provided in contact with the inner wall of the opening of the insulator 254, the insulator 244, the insulator 274, and the insulator 281, and the first conductor of the conductor 240 is provided in contact with the side surface thereof, Further inside, a second conductor of the conductor 240 is provided. Here, the height of the upper surface of the conductor 240 and the height of the upper surface of the insulator 281 can be made approximately the same. Note that although the transistor 200 shows the structure in which the first conductor of the conductor 240 and the second conductor of the conductor 240 are stacked, the present invention is not limited to this. For example, the conductor 240 may be provided as a single layer or a laminated structure of three or more layers. When the structure has a laminated structure, an ordinal number may be assigned in order of formation for distinction.

[Transistor 200]
As shown in FIG. 1, transistor 200 includes insulators 214 and 216 overlying a substrate (not shown) and conductors buried in insulators 214 and 216 . 205 (conductor 205a and conductor 205b), insulator 220 over insulator 216 and over conductor 205, insulator 222 over insulator 220, and insulator 222 Insulator 224 overlying oxide 230 (oxide 230a, oxide 230b, and oxide 230c) overlying insulator 224, and insulator 250 overlying oxide 230 , a conductor 260 (a conductor 260 a and a conductor 260 b ) provided over the insulator 250 , a conductor 242 a and a conductor 242 b in contact with part of the top surface of the oxide 230 , and a top surface of the insulator 224 . Part of it is in contact with the side surface of the oxide 230a, the side surface of the oxide 230b, the side surface of the conductor 242a, the top surface of the conductor 242a, the side surface of the conductor 242b, the top surface of the conductor 242b, and the side surface of the oxide 230c. It has an insulator 254 , an insulator 244 placed in contact with the insulator 254 , an insulator 280 placed over the insulator 244 , and an insulator 274 placed over the insulator 280 . Conductor 260 has conductor 260a and conductor 260b, and conductor 260a is arranged so as to wrap the bottom and side surfaces of conductor 260b. Here, as shown in FIG. 1B, the top surface of the conductor 260 is substantially aligned with the top surface of the insulator 254, the top surface of the insulator 244, and the top surface of the oxide 230c. Further, the insulator 274 is in contact with the top surface of the conductor 260, the top surface of the insulator 254, the top surface of the insulator 244, and the top surface of the oxide 230c.

Here, the conductor 242 a and the conductor 242 b may be collectively referred to as the conductor 242 . Conductor 242 includes a first element and a second element. The first element has higher oxidation resistance than the second element, and is, for example, one or more of Ru, Rh, Pd, Os, Ir, and Pt. Also, the second element has a work function smaller than that of the first element, such as Al, Si, Ti, Hf, Zr, Mn, In, Ga, Bi, Ta, Nb, Zn, Sn, Cu, Cr, Any one or more of W, Mo, Ge, Ni, Sc, Y, and Ce. Since the conductor 242 contains the first element with high oxidation resistance and the second element with a low work function, the conductor 242 is not oxidized by oxygen diffused from the insulator 250 or the like. can be suppressed and an ohmic contact can be made between the conductor 242 and the oxide 230 .

Further, the insulator 222, the insulator 254, the insulator 244, and the insulator 274 preferably have at least one function of suppressing diffusion of hydrogen (eg, hydrogen atoms, hydrogen molecules, or the like). For example, insulators 222 , 254 , 244 , and 274 preferably have lower hydrogen permeability than insulators 224 , 250 , and 280 . Further, the insulator 222, the insulator 254, and the insulator 244 preferably have at least one function of suppressing diffusion of oxygen (eg, oxygen atoms, oxygen molecules, or the like). For example, insulators 222 , 254 , and 244 preferably have lower oxygen permeability than insulators 224 , 250 , and 280 .

The insulator 254 includes the top and side surfaces of the conductor 242a, the top and side surfaces of the conductor 242b, the side surfaces of the oxides 230a and 230b, and the top surface of the insulator 224, as illustrated in FIGS. contact is preferred. In addition, as shown in FIGS. 1B and 1C, the insulator 244 preferably contacts top and side surfaces of the conductor 260, side surfaces of the insulator 250, and top surface of the insulator 254. FIG. Insulator 280 is thereby separated from insulator 224 , oxide 230 , and insulator 250 by insulator 254 or insulator 244 .

In addition, oxide 230 includes oxide 230a over insulator 224, oxide 230b over oxide 230a, and oxide 230b overlying oxide 230b, and at least a portion of oxide 230b is overlying oxide 230b. and oxide 230c contacting the top surface of 230b.

Note that in the transistor 200, a region where a channel is formed (hereinafter also referred to as a channel formation region) and a structure in which three layers of an oxide 230a, an oxide 230b, and an oxide 230c are stacked in the vicinity thereof are shown. However, the present invention is not limited to this. For example, a single layer of the oxide 230b, a two-layer structure of the oxides 230b and 230a, a two-layer structure of the oxides 230b and 230c, or a stacked structure of four or more layers may be employed. In addition, although the conductor 260 has a two-layer structure in the transistor 200, the present invention is not limited to this. For example, the conductor 260 may have a single-layer structure or a laminated structure of three or more layers.

Here, the conductor 260 functions as a gate electrode of the transistor, and the conductors 242a and 242b function as source and drain electrodes, respectively. The conductor 260 preferably has a region overlapping with the conductor 242a with the insulator 250 interposed therebetween and a region overlapping with the conductor 242b with the insulator 250 interposed therebetween. By forming the conductor 260 in such a shape, the conductor 260 can have an alignment margin, so that the conductor 260 is formed in the region between the conductor 242a and the conductor 242b of the oxide 230. can be reliably superimposed.

Note that, as shown in FIG. 1, the conductor 260 preferably has a conductor 260a and a conductor 260b arranged over the conductor 260a.

In addition, the transistor 200 includes an insulator 214 provided over a substrate (not shown), an insulator 216 provided over the insulator 214, and the insulator 214 and the insulator 216. and an insulator 216 and an insulator 220 disposed over the conductor 205 . Furthermore, insulator 222 is preferably disposed over insulator 220 .

In the transistor 200, a metal oxide functioning as an oxide semiconductor (hereinafter also referred to as an oxide semiconductor) is added to the oxide 230 (the oxide 230a, the oxide 230b, and the oxide 230c) including the channel formation region. It is preferable to use

Since the transistor 200 including an oxide semiconductor for a channel formation region has extremely low leakage current (off-state current) in a non-conducting state, a semiconductor device with low power consumption can be provided. Further, since an oxide semiconductor can be deposited by a sputtering method or the like, it can be used for the transistor 200 included in a highly integrated semiconductor device.

For example, as the oxide 230, an In-M-Zn oxide (element M is aluminum, gallium, yttrium, tin, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium , neodymium, hafnium, tantalum, tungsten, or magnesium) or the like) may be used. In particular, the element M is preferably aluminum, gallium, yttrium, or tin. Alternatively, as the oxide 230, an In--Ga oxide or an In--Zn oxide may be used.

In addition, when impurities and oxygen vacancies are present in a region where a channel is formed in the oxide semiconductor, electrical characteristics of a transistor using an oxide semiconductor are likely to fluctuate, and reliability may be degraded. In addition, when oxygen vacancies are included in a region where a channel is formed in the oxide semiconductor, the transistor tends to have normally-on characteristics. Therefore, oxygen vacancies in the region where the channel is formed are preferably reduced as much as possible. For example, oxygen may be supplied to the oxide 230 through the insulator 250 or the like to fill oxygen vacancies. Accordingly, it is possible to provide a transistor having stable electrical characteristics and improved reliability by suppressing variation in electrical characteristics.

Further, an element (eg, a second element) included in the conductors 242 (the conductors 242a and 242b) that is provided over and in contact with the oxide 230 and functions as a source electrode and a drain electrode is an oxide. If the oxide 230 has a function of absorbing oxygen, a low resistance region may be partially formed between the oxide 230 and the conductor 242 or near the surface of the oxide 230 . In this case, impurities (hydrogen, nitrogen, metal element, or the like) entering the oxygen vacancies may function as donors in the low-resistance region, increasing the carrier density. Note that, hereinafter, the hydrogen that enters the oxygen vacancies may be referred to as _VoH .

Here, FIG. 2A is an enlarged view of part of the transistor 200 shown in FIGS. 1A and 2A is an enlarged view of part of the transistor 200A in which the conductor 242 does not contain the first element. B). As shown in FIGS. 2A and 2B, a conductor 242 is provided on and in contact with the oxide 230, and the interface of the oxide 230 with the conductor 242 and its vicinity are provided as low-resistance regions. Regions 243 (regions 243a and 243b) may be formed. Oxide 230 has a region 234 that functions as a channel forming region of transistor 200 and a region 231 (regions 231a and 231b) that includes part of region 243 and functions as a source or drain region. It should be noted that in subsequent drawings, even if the region 243 is not shown in an enlarged view or the like, the same region 243 may be formed.

As shown in FIG. 2B, in the transistor 200A, oxygen 291 contained in the insulator 250 is supplied to the region 234, so that oxygen vacancies in the region 234 can be reduced. However, in the conductor 242 of the transistor 200A, which does not contain the first element and has low oxidation resistance, the oxygen 291 is absorbed in and near the side surfaces of the conductors 242a and 242b which are in contact with the insulator 250. An oxidized region 293 is formed near the side surface of the conductor 242 . As shown in FIG. 2B, the region 293 may be formed not only on the side surface of the conductor 242 but also on the lower surface near the side surface of the conductor 242 so as to extend horizontally with respect to the substrate. .

Thus, in the transistor 200A, the channel length L is not the designed distance between the conductors 242a and 242b, but the length ΔL in the channel direction of the regions 293 on the sides of the conductors 242a and 242b. There is a risk that it will be a rushed distance. In other words, since the region 293 substantially functions as a Loff region, the on current and frequency characteristics of the transistor 200A may decrease from the design values.

In addition, when the oxidation resistance of the conductor 242 of the transistor 200A is even lower, oxygen is excessively absorbed from the oxide 230b in contact with the lower surface of the conductor 242, and the regions 243a and 243b extend horizontally in the substrate. , the regions 243a and 243b may be connected. In this case, an extended region 243 may be formed on top of region 234 and transistor 200A may be conductive at all times.

In contrast to the transistor 200A in which the conductor 242 is easily oxidized, the transistor 200 in which the conductor 242 contains the first element has oxidation resistance against oxygen 291 contained in the insulator 250. Oxidation of the vicinity of the side surface of the conductor 242b in contact with the insulator 250 can be suppressed. As a result, the channel length L becomes the designed distance between the conductors 242a and 242b, so that it is possible to prevent the on-current and the frequency characteristics from being reduced from the design values.

In the transistor 200, the conductor 242 contains the second element. A second element may be deposited under the conductor 242, ie in region 243, to form a layer. It can also be said that layers containing the second element are formed between the conductor 242a and the oxide 230b and between the conductor 242b and the oxide 230b. The concentration of the second element in the layer containing the second element may be higher than the concentration of the second element in the conductors 242a and 242b.

When the layer containing the second element is formed under the conductor 242 in this manner, the second element with a low work function extracts oxygen from the oxide 230b to form oxygen vacancies. Impurities such as hydrogen are trapped in the oxygen vacancies, so that the vicinity of the layer containing the second element of the oxide 230b becomes n-type. Thus, a region 243 with high carrier density is formed under the conductor 242 . Note that the second element combines with oxygen extracted from the oxide 230b to form an oxide of the second element. Therefore, in the transistor 200, layers may be formed in this order from the bottom: the oxide 230b, the layer containing V _o H, the layer containing the oxide of the second element, and the conductor 242 .

Thus, in the transistor 200, the region 243 is formed with the second element. That is, the size of the region 243, the carrier density, and the like can be controlled by the amount of the second element when the conductor 242 is formed. Therefore, it is preferable to set the amount of the second element at the time of film formation as appropriate in accordance with the design of the electrical characteristics of the transistor 200 . As a result, the region 243 can be formed only in the vicinity of the conductor 242, so that a transistor with stable electrical characteristics can be provided.

Note that although the region 243a and the region 243b are provided so as to diffuse in the depth direction near the conductor 242 of the oxide 230b, the present invention is not limited to this. The regions 243a and 243b may be formed as appropriate in accordance with required electrical characteristics of the transistor. Also, in the oxide 230, it may be difficult to clearly detect boundaries between regions. The concentration of the element detected in each region (for example, the concentration of the second element) is not limited to stepwise changes for each region, but also changes continuously (also referred to as gradation) within each region. good too.

Further, as shown in FIG. 2, the thickness of the oxide 230b in a region that does not overlap with the conductor 242 is thinner than that in a region that overlaps with the conductor 242 in some cases. This is formed by removing a portion of the top surface of oxide 230b when forming conductors 242a and 242b. When a conductive film to be the conductor 242 is formed on the top surface of the oxide 230b, a region 243 with low resistance may be formed over the top surface of the region 234 in some cases. Thus, by removing region 243 located between conductors 242a and 242b on the top surface of oxide 230b, it is possible to prevent the formation of a channel in a region of low resistance on the top surface of region 234. can. In addition, in the following drawings, even if the enlarged view or the like does not show the thin film thickness region, the same thin film thickness region may be formed.

As described above, a semiconductor device including a transistor with high on-state current can be provided. Alternatively, a semiconductor device including a transistor with high frequency characteristics can be provided. Alternatively, it is possible to provide a semiconductor device in which variation in electrical characteristics is suppressed, stable electrical characteristics are obtained, and reliability is improved. Alternatively, a semiconductor device including a transistor with low off-state current can be provided.

A detailed structure of the semiconductor device including the transistor 200 according to one embodiment of the present invention is described below.

As shown in FIGS. 1A and 1C, the conductor 203 extends in the channel width direction and functions as a wiring that applies a potential to the conductor 205 . Note that the conductor 203 is preferably embedded in the insulator 212 .

Conductor 205 is arranged to overlap with oxide 230 and conductor 260 . Further, the conductor 205 is preferably provided on and in contact with the conductor 203 . Further, the conductor 205 is preferably embedded in the insulators 214 and 216 .

Here, the conductor 260 may function as a first gate (also referred to as a top gate) electrode. In some cases, the conductor 205 functions as a second gate (also referred to as a bottom gate) electrode. In that case, Vth of the transistor 200 can be controlled by changing the potential applied to the conductor 205 independently of the potential applied to the conductor 260 . In particular, by applying a negative potential to the conductor 205, Vth of the transistor 200 can be made higher than 0 V and off-state current can be reduced. Therefore, applying a negative potential to the conductor 205 can make the drain current smaller when the potential applied to the conductor 260 is 0 V than when no potential is applied.

By providing the conductor 205 over the conductor 203, the distance between the conductor 203 and the conductor 260 functioning as the first gate electrode and the wiring can be designed as appropriate. In other words, by providing the insulator 214 and the insulator 216 between the conductor 203 and the conductor 260, the parasitic capacitance between the conductor 203 and the conductor 260 is reduced, can increase the dielectric strength between By reducing the parasitic capacitance between the conductor 203 and the conductor 260, the switching speed of the transistor 200 can be improved and the transistor can have high frequency characteristics.

Note that the conductor 205 is arranged so as to overlap with the oxide 230 and the conductor 260 as shown in FIG. Also, the conductor 205 is preferably provided larger than the region 234 in the oxide 230 . In particular, as shown in FIG. 1C, it is preferable that the conductor 205 extends also in a region outside the edge of the region 234 of the oxide 230 crossing the channel width direction. In other words, the conductor 205 and the conductor 260 preferably overlap with each other with an insulator interposed therebetween on side surfaces of the oxide 230 in the channel width direction.

With the above structure, the electric field of the conductor 260 functioning as the first gate electrode and the electric field of the conductor 205 functioning as the second gate electrode electrically energize the channel formation region of the region 234 . can be surrounded by In this specification, a transistor structure in which a channel formation region is electrically surrounded by electric fields of a first gate electrode and a second gate electrode is referred to as a surrounded channel (S-channel) structure.

The conductor 205a or the first conductor of the conductor 203 contains impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (such as N ₂ O, NO, NO ₂ ), and copper atoms. It is preferable to use a conductive material that has a function of suppressing the diffusion of ions (that is, it is difficult for the above impurities to permeate). Alternatively, it is preferable to use a conductive material that has a function of suppressing at least one diffusion of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the above-mentioned oxygen is difficult to permeate). In this specification, the function of suppressing the diffusion of impurities or oxygen means the function of suppressing the diffusion of either one or all of the impurities or oxygen.

Since the conductor 205a or the first conductor of the conductor 203 has a function of suppressing diffusion of oxygen, it is possible to suppress oxidation of the conductor 205b or the conductor 203b and a decrease in conductivity. As the conductive material having a function of suppressing diffusion of oxygen, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used, for example. Therefore, as the conductor 205a or the first conductor of the conductor 203, a single layer or a laminate of the above conductive materials may be used. Accordingly, diffusion of impurities such as water or hydrogen to the transistor 200 side through the conductors 203 and 205 can be suppressed.

A conductive material containing tungsten, copper, or aluminum as its main component is preferably used for the conductor 205b. Although the conductor 205b is illustrated as a single layer, it may have a laminated structure, for example, a laminated structure of titanium, titanium nitride, and the above conductive material.

In addition, since the second conductor of the conductor 203 functions as a wiring, a conductor having higher conductivity than the conductor 205b is preferably used. For example, a conductive material containing copper or aluminum as a main component can be used. Further, the second conductor of the conductor 203 may have a layered structure, for example, a layered structure of titanium or titanium nitride and any of the above conductive materials.

In particular, it is preferable to use copper for the second conductor of the conductor 203 . Since copper has a low resistance, it is preferably used for wiring and the like. On the other hand, since copper easily diffuses, diffusion into the oxide 230 may degrade the electrical characteristics of the transistor 200 . Therefore, by using a material such as aluminum oxide or hafnium oxide, which has low copper permeability, for the insulator 214, the diffusion of copper can be suppressed.

Note that the conductor 205, the insulator 214, and the insulator 216 are not necessarily provided. In that case, part of the conductor 203 can function as the second gate electrode.

The insulator 210 and the insulator 214 preferably function as barrier insulating films that prevent impurities such as water and hydrogen from entering the transistor 200 from the substrate side. Therefore, the insulator 210 and the insulator 214 do not allow diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (such as N ₂ O, NO, NO ₂ ), and copper atoms. It is preferable to use an insulating material that has a function of suppressing (it is difficult for the above impurities to permeate). Alternatively, it is preferable to use an insulating material that has a function of suppressing at least one diffusion of oxygen (for example, oxygen atoms, oxygen molecules, etc.) (the above-mentioned oxygen is difficult to permeate).

For example, it is preferable to use aluminum oxide or the like as the insulator 210 and use silicon nitride or the like as the insulator 214 . Accordingly, impurities such as water or hydrogen can be prevented from diffusing from the substrate side to the transistor 200 side with respect to the insulators 210 and 214 . Alternatively, oxygen contained in the insulator 224 or the like can be prevented from diffusing toward the substrate side of the insulators 210 and 214 . In addition, even if a metal such as copper that is easily diffused is used for the second conductor of the conductor 203 , the metal is prevented from diffusing into a layer above the insulator 214 by providing silicon nitride or the like as the insulator 214 . can be suppressed.

The insulators 212 , 216 , 280 , and 281 that function as interlayer films preferably have a lower dielectric constant than the insulator 210 or the insulator 214 . By using a material with a low dielectric constant as the interlayer film, the parasitic capacitance generated between wirings can be reduced. For example, the insulator 212, the insulator 216, the insulator 280, and the insulator 281 include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, carbon and Nitrogen-added silicon oxide, vacant silicon oxide, or the like may be used as appropriate.

Insulator 220, insulator 222, and insulator 224 function as gate insulators.

Here, the insulator 224 in contact with the oxide 230 preferably releases oxygen by heating. In this specification, the oxygen released by heating is sometimes referred to as excess oxygen. For example, silicon oxide, silicon oxynitride, or the like may be used as appropriate for the insulator 224 . By providing an insulator containing oxygen in contact with the oxide 230, oxygen vacancies in the oxide 230 can be reduced and the reliability of the transistor 200 can be improved.

Specifically, an oxide material from which part of oxygen is released by heating is preferably used as the insulator 224 . The oxide that desorbs oxygen by heating means that the desorption amount of oxygen in terms of oxygen molecules is 1.0×10 ¹⁸ molecules/cm ³ or more, preferably 1, in TDS (Thermal Desorption Spectroscopy) analysis. 0×10 ¹⁹ molecules/cm ³ or more, more preferably 2.0×10 ¹⁹ molecules/cm ³ or 3.0×10 ²⁰ molecules/cm ³ or more. The surface temperature of the film during the TDS analysis is preferably in the range of 100° C. or higher and 700° C. or lower, or 100° C. or higher and 400° C. or lower.

Further, as shown in FIG. 1C, the thickness of the insulator 224 in a region which does not overlap with the insulator 254 and does not overlap with the oxide 230b may be thinner than the thickness of the other regions. . A region of the insulator 224 which does not overlap with the insulator 254 and does not overlap with the oxide 230b preferably has a thickness with which oxygen can be diffused sufficiently.

Like the insulator 210 and the like, the insulator 222 preferably functions as a barrier insulating film that prevents impurities such as water and hydrogen from entering the transistor 200 from the substrate side. For example, insulator 222 preferably has a lower hydrogen permeability than insulator 224 . By surrounding the insulator 224, the oxide 230, the insulator 250, and the like with the insulator 222, the insulator 254, and the insulator 244, impurities such as water and hydrogen are prevented from entering the transistor 200 from the outside. can do.

Further, the insulator 222 preferably has a function of suppressing diffusion of at least one of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). For example, insulator 222 preferably has a lower oxygen permeability than insulator 224 . The insulator 222 preferably has a function of suppressing diffusion of oxygen and impurities, so that diffusion of oxygen in the oxide 230 to the insulator 220 side can be reduced. In addition, the conductor 205 can be prevented from reacting with oxygen contained in the insulator 224 or the oxide 230 .

The insulator 222 preferably contains an oxide of one or both of aluminum and hafnium, which are insulating materials. As the insulator containing oxide of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. When the insulator 222 is formed using such a material, the insulator 222 suppresses release of oxygen from the oxide 230 and entry of impurities such as hydrogen from the periphery of the transistor 200 into the oxide 230. act as a layer.

Alternatively, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide may be added to these insulators. Alternatively, these insulators may be nitrided. Silicon oxide, silicon oxynitride, or silicon nitride may be stacked over the above insulator.

The insulator 222 is made of, for example, aluminum oxide, hafnium oxide, tantalum oxide, zirconium oxide, lead zirconate titanate (PZT), strontium titanate (SrTiO ₃ ) or (Ba,Sr)TiO ₃ (BST). Insulators containing so-called high-k materials may be used in single layers or stacks. As transistors are miniaturized and highly integrated, thinning of gate insulators may cause problems such as leakage current. By using a high-k material for the insulator that functions as a gate insulator, it is possible to reduce the gate potential during transistor operation while maintaining the physical film thickness.

Insulator 220 is also preferably thermally stable. For example, silicon oxide and silicon oxynitride are thermally stable. Therefore, by combining an insulator made of a high-k material and the insulator 220, a thermally stable laminated structure with a high relative dielectric constant can be obtained. can be done.

Note that the insulator 220, the insulator 222, and the insulator 224 may have a stacked structure of two or more layers. In that case, it is not limited to a laminated structure made of the same material, and a laminated structure made of different materials may be used. Alternatively, the insulator 220 may not be provided, and only the insulators 222 and 224 may be provided.

Oxide 230 has oxide 230a, oxide 230b over oxide 230a, and oxide 230c over oxide 230b. By providing the oxide 230a under the oxide 230b, diffusion of impurities from a structure formed below the oxide 230a to the oxide 230b can be suppressed. In addition, by having the oxide 230c over the oxide 230b, diffusion of impurities from a structure formed above the oxide 230c to the oxide 230b can be suppressed.

Note that the oxide 230 preferably has a layered structure with oxides having different atomic ratios of metal atoms. Specifically, in the metal oxide used for the oxide 230a, the atomic number ratio of the element M among the constituent elements is greater than the atomic number ratio of the element M among the constituent elements in the metal oxide used for the oxide 230b. is preferred. Moreover, in the metal oxide used for the oxide 230a, the atomic ratio of the element M to In is preferably higher than the atomic ratio of the element M to In in the metal oxide used for the oxide 230b. In addition, the atomic ratio of In to the element M in the metal oxide used for the oxide 230b is preferably higher than the atomic ratio of In to the element M in the metal oxide used for the oxide 230a. In addition, the oxide 230c can be a metal oxide that can be used for the oxide 230a or the oxide 230b.

Further, the oxide 230b preferably has crystallinity. For example, CAAC-OS (c-axis aligned crystal oxide semiconductor), which will be described later, is preferably used. A crystalline oxide such as CAAC-OS has few impurities and defects (such as oxygen vacancies) and has a dense structure with high crystallinity. Therefore, extraction of oxygen from the oxide 230b by the source electrode or the drain electrode can be suppressed. Accordingly, extraction of oxygen from the oxide 230b can be reduced even if heat treatment is performed, so that the transistor 200 is stable against high temperatures (so-called thermal budget) in the manufacturing process.

In addition, it is preferable that the energies of the conduction band bottoms of the oxides 230a and 230c be higher than the energies of the conduction band bottoms of the oxide 230b. Also, in other words, the electron affinities of the oxides 230a and 230c are preferably smaller than the electron affinities of the oxide 230b.

Here, the energy level at the bottom of the conduction band changes smoothly at the junction of the oxide 230a, the oxide 230b, and the oxide 230c. In other words, it can be said that the energy level of the bottom of the conduction band at the junction of the oxide 230a, the oxide 230b, and the oxide 230c continuously changes or continuously joins. In order to achieve this, the defect level density of the mixed layers formed at the interface between the oxides 230a and 230b and at the interface between the oxides 230b and 230c should be reduced.

Specifically, the oxide 230a and the oxide 230b, and the oxide 230b and the oxide 230c have a common element (main component) other than oxygen, thereby forming a mixed layer with a low defect level density. can do. For example, when the oxide 230b is an In--Ga--Zn oxide, the oxides 230a and 230c may be In--Ga--Zn oxide, Ga--Zn oxide, gallium oxide, or the like.

Specifically, a metal oxide of In:Ga:Zn=1:3:4 [atomic ratio] or 1:1:0.5 [atomic ratio] may be used as the oxide 230a. As the oxide 230b, a metal oxide of In:Ga:Zn=4:2:3 [atomic ratio] or 3:1:2 [atomic ratio] may be used. As the oxide 230c, a metal oxide of In:Ga:Zn=4:2:3 [atomic ratio] or 3:1:2 [atomic ratio] may be used. Alternatively, indium tin oxide containing silicon may be used as the oxide 230c.

At this time, the main path of carriers is the oxide 230b. When the oxides 230a and 230c have the above structures, defect level densities at the interfaces between the oxides 230a and 230b and between the oxides 230b and 230c can be reduced. Therefore, the influence of interface scattering on carrier conduction is reduced, and the transistor 200 can obtain high on-current and high frequency characteristics.

A metal oxide that functions as an oxide semiconductor is preferably used for the oxide 230 . For example, it is preferable to use a metal oxide having a bandgap of 2 eV or more, preferably 2.5 eV or more, as the metal oxide that becomes the region 234 . By using a metal oxide with a large bandgap in this manner, off-state current of a transistor can be reduced. By using such a transistor, a semiconductor device with low power consumption can be provided.

A conductor 242 (a conductor 242a and a conductor 242b) functioning as a source electrode and a drain electrode is provided over the oxide 230b. The thickness of the conductor 242 may be, for example, 1 nm or more and 50 nm or less, preferably 2 nm or more and 25 nm or less. The conductor 242 includes a first element having higher oxidation resistance than the second element and a second element having a lower work function than the first element. The conductor 242 may be a compound containing the first element or the second element as a main component, may be an alloy of the first element and the second element, or may be an alloy of the first element and the second element. It may be a conductive oxide containing or a conductive nitride containing the first element and the second element.

Since the first element has high oxidation resistance, oxidation of the conductor 242, reduction of the insulator 250, and reduction of the oxide 230 can be suppressed. As such a first element, it is preferable to use a platinum group element with low reactivity to acid. Just do it. In particular, ruthenium has a relatively small work function among the platinum group elements, so it is easy to reduce the work function of the conductor 242 and is suitable.

Since the second element has a small work function, it can reduce the work function difference between the conductor 242 and the oxide 230 and form an ohmic contact with the oxide 230 . For example, when miniaturizing the transistor 200 for LSI, the work function may be about 5.2 eV if the conductor 242 is made of only ruthenium. Therefore, for example, the second element preferably has a work function of 5.2 eV or less. Examples of such second elements include aluminum, silicon, titanium, hafnium, zirconium, manganese, indium, gallium, bismuth, tantalum, niobium, zinc, tin, copper, chromium, tungsten, molybdenum, germanium, nickel, Any one or more of scandium, yttrium, and cerium may be used. As noted above, oxides of the second element may form in regions 243 shown in FIG. Therefore, by using an element whose oxide has conductivity, such as titanium, as the second element, the contact resistance between the conductor 242 and the oxide 230 can be further reduced.

The oxidation resistance of the first element and the second element is evaluated, for example, by heat-treating a thin film of the first element or the second element in an oxygen-containing atmosphere and measuring the oxide of the thin film with a sheet resistance measuring instrument or the like. It can be evaluated by measuring. In this case, if the sheet resistance value of the thin film of the first element is lower than the sheet resistance value of the thin film of the second element, the oxidation resistance of the first element is higher than that of the second element. can be done. Alternatively, for example, the oxidation resistance of the first element and the second element can be evaluated by measuring the oxidation-reduction potential of the metal electrode of the first element or the second element. In this case, if the oxidation-reduction potential of the first element is higher than the oxidation-reduction potential of the second element, it can be said that the oxidation resistance of the first element is higher than that of the second element. In other words, it can be said that the ionization tendency of the first element is lower than that of the second element.

The work functions of the first element and the second element can be measured, for example, by photoelectron spectroscopy of a thin film of the first element or the second element. For example, AC-3 manufactured by Riken Keiki Co., Ltd. may be used for measurement.

Like the insulator 210 and the like, the insulator 254 preferably functions as a barrier insulating film that prevents impurities such as water and hydrogen from entering the transistor 200 from the insulator 280 side. For example, insulator 254 preferably has a lower hydrogen permeability than insulator 224 . 1B and 1C, the insulator 254 includes the top and side surfaces of the conductor 242a, the top and side surfaces of the conductor 242b, the side surfaces of the oxides 230a and 230b, and the insulator 224. is preferably in contact with the upper surface of the Such a structure prevents hydrogen contained in the insulator 280 from entering the oxide 230 from the top surface or the side surface of the conductor 242a, the conductor 242b, the oxide 230a, the oxide 230b, and the insulator 224. can be suppressed.

Further, the insulator 254 preferably has a function of suppressing at least one diffusion of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the above-mentioned oxygen is difficult to permeate). For example, insulator 254 preferably has a lower oxygen permeability than insulator 224 .

The insulator 254 is preferably deposited using a sputtering method. By forming the insulator 254 by a sputtering method in an atmosphere containing oxygen, oxygen can be added to the vicinity of a region of the insulator 224 which is in contact with the insulator 254 . Accordingly, oxygen can be supplied from the region to the oxide 230 through the insulator 224 . Here, the insulator 254 has a function of suppressing upward diffusion of oxygen, so that diffusion of oxygen from the oxide 230 to the insulator 280 can be prevented. In addition, since the insulator 222 has a function of suppressing diffusion of oxygen downward, diffusion of oxygen from the oxide 230 to the insulator 220 can be prevented. Oxygen is thus supplied to region 234 , which functions as a channel-forming region of oxide 230 . Accordingly, oxygen vacancies in the oxide 230 can be reduced, and the normally-on state of the transistor can be suppressed.

As the insulator 254, for example, an insulator containing an oxide of one or both of aluminum and hafnium is preferably deposited. Note that as the insulator containing oxides of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used.

In addition, as shown in FIGS. 1A and 1C, the side surface of the oxide 230 is covered with the conductor 260 in the region of the oxide 230b which does not overlap with the conductor 242, in other words, the channel formation region of the oxide 230. are arranged as This makes it easier for the electric field of the conductor 260 functioning as the first gate electrode to act on the side surfaces of the oxide 230 . Therefore, the on current of the transistor 200 can be increased and the frequency characteristics can be improved.

Insulator 250 functions as a gate insulator. Insulator 250 is preferably placed in contact with the top surface of oxide 230c. For the insulator 250, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, or silicon oxide having vacancies is used. be able to. In particular, silicon oxide and silicon oxynitride are preferable because they are stable against heat.

As with the insulator 224, the insulator 250 is preferably formed using an insulator from which oxygen is released by heating. By providing an insulator from which oxygen is released by heating as the insulator 250 in contact with the top surface of the oxide 230c, oxygen can be effectively supplied to the region 234 of the oxide 230b. Further, similarly to the insulator 224, the concentration of impurities such as water or hydrogen in the insulator 250 is preferably reduced. The thickness of the insulator 250 is preferably 1 nm or more and 20 nm or less.

Alternatively, a metal oxide may be provided between the insulator 250 and the conductor 260 . The metal oxide preferably suppresses oxygen diffusion from the insulator 250 to the conductor 260 . By providing the metal oxide that suppresses diffusion of oxygen, diffusion of oxygen from the insulator 250 to the conductor 260 is suppressed. That is, reduction in the amount of oxygen supplied to the oxide 230 can be suppressed. In addition, oxidation of the conductor 260 by oxygen in the insulator 250 can be suppressed.

The metal oxide may also function as part of the gate insulator. Therefore, when silicon oxide, silicon oxynitride, or the like is used for the insulator 250, the metal oxide is preferably a high-k material with a high dielectric constant. When the gate insulator has a stacked-layer structure of the insulator 250 and the metal oxide, the stacked-layer structure can be stable against heat and have a high relative dielectric constant. Therefore, the gate potential applied during transistor operation can be reduced while maintaining the physical film thickness of the gate insulator. Also, the equivalent oxide thickness (EOT) of the insulator that functions as the gate insulator can be reduced.

Specifically, a metal oxide containing one or more selected from hafnium, aluminum, gallium, yttrium, zirconium, tungsten, titanium, tantalum, nickel, germanium, magnesium, or the like can be used. can. In particular, it is preferable to use aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate), which is an insulator containing oxides of one or both of aluminum and hafnium.

Although the conductor 260 is shown as having a two-layer structure in FIG. 1, it may have a single-layer structure or a laminated structure of three or more layers.

Like the conductor 205a, the conductor 260a prevents diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (such as N ₂ O, NO, and NO ₂ ), and copper atoms. It is preferable to use a conductive material having a suppressing function. Alternatively, it is preferable to use a conductive material that has a function of suppressing at least one diffusion of oxygen (eg, oxygen atoms, oxygen molecules, etc.).

In addition, since the conductor 260a has a function of suppressing the diffusion of oxygen, it is possible to suppress oxidation of the conductor 260b due to oxygen contained in the insulator 250 and a decrease in conductivity. As the conductive material having a function of suppressing diffusion of oxygen, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like is preferably used, for example.

Conductor 260b is preferably made of a conductive material containing tungsten, copper, or aluminum as its main component. In addition, since the conductor 260 also functions as a wiring, a conductor with high conductivity is preferably used. For example, a conductive material whose main component is tungsten, copper, or aluminum can be used. Further, the conductor 260b may have a layered structure, for example, a layered structure of titanium, titanium nitride, and any of the above conductive materials.

Like the insulator 210 and the like, the insulator 244 preferably functions as a barrier insulating film that prevents impurities such as water and hydrogen from entering the transistor 200 from the insulator 280 side. For example, insulator 244 preferably has a lower hydrogen permeability than insulator 224 . Further, the insulator 244 is preferably placed in contact with the insulator 254 as shown in FIGS. With such a structure, hydrogen contained in the insulator 280 can be prevented from entering the oxide 230 from the side surfaces of the conductor 260, the oxide 230c, and the insulator 250. FIG.

In this manner, the insulator 224, the insulator 250, and the oxide 230 are covered with the insulator 254 and the insulator 244 having a barrier property against hydrogen, so that the insulator 280 can be the insulator 254 or the insulator 244. are separated from the insulator 224, the oxide 230, and the insulator 250 by As a result, entry of impurities such as hydrogen from the outside of the transistor 200 can be suppressed, so that the transistor 200 can have good electrical characteristics and reliability.

Further, the insulator 244 preferably has a function of suppressing diffusion of at least one of oxygen (eg, oxygen atoms, oxygen molecules, etc.) (the above oxygen is difficult to permeate). For example, insulator 244 preferably has a lower oxygen permeability than insulator 224 . Since the insulator 244 has a function of suppressing diffusion of oxygen, reaction of the conductor 260 with oxygen contained in the insulator 280 can be suppressed.

As the insulator 244, an insulator containing aluminum nitride may be used, for example. As the insulator 244, it is preferable to use a nitride insulator satisfying a composition formula AlNx (x is a real number greater than 0 and less than or equal to 2, preferably x is a real number greater than 0.5 and less than or equal to 1.5). Accordingly, a film having excellent insulating properties and excellent thermal conductivity can be formed, so that the heat dissipation property of the transistor 200 when it is driven can be improved. Alternatively, as the insulator 244, aluminum titanium nitride, titanium nitride, or the like can be used. In this case, a film can be formed by sputtering without using a highly oxidizing gas such as oxygen or ozone as a film forming gas, which is preferable.

As the insulator 244, for example, an insulator containing an oxide of one or both of aluminum and hafnium is preferably deposited. Note that as the insulator containing oxides of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. In this case, insulator 244 is preferably deposited using ALD. Since the ALD method is a film formation method with good coverage, it is possible to prevent the formation of discontinuities due to unevenness of the insulator 244 .

The insulator 280 is provided over the insulator 224 , the oxide 230 , the conductor 242 , the insulator 250 , and the conductor 260 with the insulator 244 interposed therebetween. For example, the insulator 280 is formed using silicon oxide, silicon oxynitride, silicon nitride oxide, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, silicon oxide having vacancies, or the like. It is preferable to have In particular, silicon oxide and silicon oxynitride are preferable because they are thermally stable. In particular, a material such as silicon oxide, silicon oxynitride, or silicon oxide having vacancies is preferable because a region containing oxygen that is released by heating can be easily formed.

It is preferable that the concentration of impurities such as water or hydrogen in the insulator 280 is reduced. Also, the upper surface of the insulator 280 may be flattened.

Like the insulator 210 and the like, the insulator 274 preferably functions as a barrier insulating film that prevents impurities such as water or hydrogen from entering the insulator 280 from above. As the insulator 274, an insulator that can be used for the insulator 210, the insulator 254, or the like may be used, for example.

An insulator 281 functioning as an interlayer film is preferably provided over the insulator 274 . As with the insulator 224 and the like, the insulator 281 preferably has a reduced concentration of impurities such as water or hydrogen in the film.

In addition, the conductors 240 a and 240 b are arranged in openings formed in the insulators 281 , 274 , 280 , and 244 . The conductor 240a and the conductor 240b are provided to face each other with the conductor 260 interposed therebetween. Note that the top surfaces of the conductors 240 a and 240 b may be flush with the top surface of the insulator 281 .

Note that the insulator 241a is provided in contact with the inner walls of the openings of the insulators 281, 274, 280, and 244, and the first conductor of the conductor 240a is formed in contact with the side surface thereof. ing. A conductor 242a is positioned at least part of the bottom of the opening, and the conductor 240a is in contact with the conductor 242a. Similarly, the insulator 241b is provided in contact with the inner walls of the openings of the insulator 281, the insulator 274, the insulator 280, and the insulator 244, and the first conductor of the conductor 240b is formed in contact with the side surface thereof. It is A conductor 242b is positioned at least part of the bottom of the opening, and the conductor 240b is in contact with the conductor 242b.

A conductive material containing tungsten, copper, or aluminum as its main component is preferably used for the conductors 240a and 240b. Further, the conductor 240a and the conductor 240b may have a laminated structure.

In the case where the conductor 240 has a layered structure, the conductors in contact with the oxide 230a, the oxide 230b, the conductor 242, the insulator 244, the insulator 280, the insulator 274, and the insulator 281 include the conductor 205a and the like. Similarly to , it is preferable to use a conductive material having a function of suppressing permeation of impurities such as water or hydrogen. For example, tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, ruthenium oxide, or the like is preferably used. In addition, the conductive material having a function of suppressing permeation of impurities such as water or hydrogen may be used in a single layer or a stacked layer. By using the conductive material, oxygen added to the insulator 280 can be prevented from being absorbed by the conductors 240a and 240b. In addition, impurities such as water or hydrogen from a layer above the insulator 281 can be prevented from entering the oxide 230 through the conductors 240a and 240b.

As the insulator 241a and the insulator 241b, an insulator that can be used for the insulator 244 or the like may be used, for example. Since the insulators 241a and 241b are provided in contact with the insulators 254 and 244, impurities such as water or hydrogen from the insulator 280 or the like enter the oxide 230 through the conductors 240a and 240b. can be suppressed. In addition, oxygen contained in the insulator 280 can be prevented from being absorbed by the conductors 240a and 240b.

Further, although not illustrated, a conductor functioning as a wiring may be arranged in contact with the upper surface of the conductor 240a and the upper surface of the conductor 240b. A conductive material containing tungsten, copper, or aluminum as a main component is preferably used for the conductor functioning as the wiring. Further, the conductor may have a layered structure, for example, a layered structure of titanium, titanium nitride, and the above conductive material. Note that the conductor may be formed so as to be embedded in an opening provided in the insulator, similarly to the conductor 203 and the like.

<Semiconductor Device Constituent Material>
Constituent materials that can be used for the semiconductor device are described below.

<<Substrate>>
As a substrate for forming the transistor 200, an insulator substrate, a semiconductor substrate, or a conductor substrate may be used, for example. Examples of insulator substrates include glass substrates, quartz substrates, sapphire substrates, stabilized zirconia substrates (yttria stabilized zirconia substrates, etc.), and resin substrates. Examples of semiconductor substrates include semiconductor substrates such as silicon and germanium, and compound semiconductor substrates made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, and gallium oxide. Further, there is a semiconductor substrate having an insulator region inside the semiconductor substrate, such as an SOI (Silicon On Insulator) substrate. Examples of conductive substrates include graphite substrates, metal substrates, alloy substrates, and conductive resin substrates. Alternatively, there are a substrate having a metal nitride, a substrate having a metal oxide, and the like. Furthermore, there are substrates in which an insulator substrate is provided with a conductor or a semiconductor, a substrate in which a semiconductor substrate is provided with a conductor or an insulator, a substrate in which a conductor substrate is provided with a semiconductor or an insulator, and the like. Alternatively, these substrates provided with elements may be used. Elements provided on the substrate include a capacitor element, a resistance element, a switch element, a light emitting element, a memory element, and the like.

<<insulator>>
As insulators, there are insulating oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, metal nitride oxides, and the like.

For example, as transistors are miniaturized and highly integrated, thinning of gate insulators may cause problems such as leakage current. By using a high-k material for the insulator that functions as the gate insulator, it is possible to reduce the voltage during transistor operation while maintaining the physical film thickness. On the other hand, by using a material having a low dielectric constant as an insulator functioning as an interlayer film, the parasitic capacitance generated between wirings can be reduced. Therefore, the material should be selected according to the function of the insulator.

Insulators with a high relative dielectric constant include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, and silicon and hafnium. oxynitrides with silicon, or nitrides with silicon and hafnium.

Insulators with a low relative dielectric constant include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, and an empty silicon oxide. There are silicon oxide with pores, resin, and the like.

In addition, a transistor including an oxide semiconductor includes insulators (the insulator 210, the insulator 214, the insulator 222, the insulator 254, the insulator 244, and the insulator 210, the insulator 214, the insulator 222, the insulator 254, and the insulator 244) that have a function of suppressing permeation of impurities such as hydrogen and oxygen. The electrical characteristics of the transistor can be stabilized by surrounding it with a body 274 or the like. Examples of insulators having a function of suppressing permeation of impurities such as hydrogen and oxygen include boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, and zirconium. Insulators including lanthanum, neodymium, hafnium, or tantalum may be used in single layers or in stacks. Specifically, as insulators having a function of suppressing permeation of impurities such as hydrogen and oxygen, aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, Alternatively, a metal oxide such as tantalum oxide, or a metal nitride such as aluminum nitride, aluminum titanium nitride, titanium nitride, silicon nitride oxide, or silicon nitride can be used.

An insulator that functions as a gate insulator preferably has a region containing oxygen that is released by heating. For example, by forming a structure in which silicon oxide or silicon oxynitride having a region containing oxygen released by heating is in contact with the oxide 230, oxygen vacancies in the oxide 230 can be compensated.

<<Conductor>>
Conductors include aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum. It is preferable to use a metal element selected from among the above, an alloy containing the above-described metal elements as a component, or an alloy or the like in which the above-described metal elements are combined. For example, tantalum nitride, titanium nitride, tungsten, nitride containing titanium and aluminum, nitride containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxide containing strontium and ruthenium, oxide containing lanthanum and nickel, and the like are used. is preferred. Also, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are difficult to oxidize. It is preferable because it is a conductive material or a material that maintains conductivity even after absorbing oxygen. Alternatively, a semiconductor with high electrical conductivity, typified by polycrystalline silicon containing an impurity element such as phosphorus, or a silicide such as nickel silicide may be used.

Alternatively, a plurality of conductive layers formed using any of the above materials may be stacked and used. For example, a laminated structure in which the material containing the metal element described above and the conductive material containing oxygen are combined may be used. Alternatively, a laminated structure may be employed in which the material containing the metal element described above and the conductive material containing nitrogen are combined. Alternatively, a laminated structure may be employed in which the material containing the metal element described above, the conductive material containing oxygen, and the conductive material containing nitrogen are combined.

Note that in the case where an oxide is used for a channel formation region of a transistor, a stacked-layer structure in which the above-described material containing the metal element and a conductive material containing oxygen are combined is used for a conductor functioning as a gate electrode. is preferred. In this case, a conductive material containing oxygen is preferably provided on the channel formation region side. By providing the conductive material containing oxygen on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.

In particular, a conductive material containing oxygen and a metal element contained in a metal oxide in which a channel is formed is preferably used as a conductor functioning as a gate electrode. Alternatively, a conductive material containing the metal element and nitrogen described above may be used. For example, a conductive material containing nitrogen such as titanium nitride or tantalum nitride may be used. Further, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, and silicon were added. Indium tin oxide may also be used. Alternatively, indium gallium zinc oxide containing nitrogen may be used. By using such a material, hydrogen contained in the metal oxide in which the channel is formed can be captured in some cases. Alternatively, it may be possible to capture hydrogen mixed from an outer insulator or the like.

<<metal oxide>>
A metal oxide that functions as an oxide semiconductor is preferably used as the oxide 230 . Metal oxides applicable to the oxide 230 according to the present invention are described below.

The metal oxide preferably contains at least indium or zinc. In particular, it preferably contains indium and zinc. In addition, aluminum, gallium, yttrium, tin, or the like is preferably contained. Further, one or more selected from boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc. may be contained.

Consider here the case where the metal oxide is an In--M--Zn oxide with indium, the element M and zinc. Note that the element M is aluminum, gallium, yttrium, tin, or the like. Other elements applicable to element M include boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, and magnesium. However, as the element M, there are cases where a plurality of the above elements may be combined.

In this specification and the like, metal oxides containing nitrogen may also be collectively referred to as metal oxides. Metal oxides containing nitrogen may also be referred to as metal oxynitrides.

[Structure of Metal Oxide]
Oxide semiconductors (metal oxides) are classified into single-crystal oxide semiconductors and non-single-crystal oxide semiconductors. Non-single-crystal oxide semiconductors include, for example, CAAC-OS (c-axis aligned crystalline oxide semiconductor), polycrystalline oxide semiconductors, nc-OS (nanocrystalline oxide semiconductors), pseudo-amorphous oxide semiconductors (a-like (OS: amorphous-like oxide semiconductor), amorphous oxide semiconductor, and the like.

CAAC-OS has a c-axis orientation and a distorted crystal structure in which a plurality of nanocrystals are connected in the ab plane direction. The strain refers to a portion where the orientation of the lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement in a region where a plurality of nanocrystals are connected.

Although nanocrystals are basically hexagonal, they are not limited to regular hexagons and may have non-regular hexagons. Also, the distortion may have a lattice arrangement of pentagons, heptagons, and the like. In CAAC-OS, it is difficult to confirm clear crystal grain boundaries (also called grain boundaries) even in the vicinity of strain. That is, it can be seen that the distortion of the lattice arrangement suppresses the formation of grain boundaries. This is because the CAAC-OS can tolerate strain due to the fact that the arrangement of oxygen atoms is not dense in the ab plane direction and the bond distance between atoms changes due to the substitution of metal elements. It's for.

CAAC-OS is a layered crystal in which a layer containing indium and oxygen (hereinafter referred to as an In layer) and a layer containing the element M, zinc, and oxygen (hereinafter referred to as a (M, Zn) layer) are stacked. It tends to have a structure (also called a layered structure). Note that indium and the element M can be substituted with each other, and when the element M in the (M, Zn) layer is substituted with indium, the layer can also be expressed as an (In, M, Zn) layer. In addition, when indium in the In layer is replaced with the element M, it can also be expressed as an (In, M) layer.

CAAC-OS is a highly crystalline metal oxide. On the other hand, in CAAC-OS, since it is difficult to confirm a clear crystal grain boundary, it can be said that the decrease in electron mobility due to the crystal grain boundary is unlikely to occur. In addition, since the crystallinity of metal oxides may be degraded by the contamination of impurities and the generation of defects, CAAC-OS is made of a metal with few impurities and defects (such as oxygen vacancy (V _O )). It can also be called an oxide. Therefore, metal oxides with CAAC-OS have stable physical properties. Therefore, a metal oxide containing CAAC-OS is heat resistant and highly reliable.

The nc-OS has periodic atomic arrangement in a minute region (eg, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). Also, nc-OS shows no regularity in crystal orientation between different nanocrystals. Therefore, no orientation is observed in the entire film. Therefore, an nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor depending on the analysis method.

Note that indium-gallium-zinc oxide (hereinafter referred to as IGZO), which is a type of metal oxide containing indium, gallium, and zinc, may have a stable structure when formed into the above-described nanocrystals. be. In particular, since IGZO tends to be difficult to crystallize in the atmosphere, it is better to use smaller crystals (for example, the above-mentioned nanocrystals) than large crystals (here, crystals of several mm or crystals of several cm). can be structurally stable.

An a-like OS is a metal oxide having a structure between an nc-OS and an amorphous oxide semiconductor. An a-like OS has void or low density regions. That is, a-like OS has lower crystallinity than nc-OS and CAAC-OS.

Oxide semiconductors (metal oxides) have various structures, each of which has different characteristics. An oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, an nc-OS, and a CAAC-OS.

[impurities]
Here, the effect of each impurity in the metal oxide will be described.

Further, if the metal oxide contains an alkali metal or an alkaline earth metal, it may form a defect level and generate carriers. Therefore, a transistor in which a metal oxide containing an alkali metal or an alkaline earth metal is used for a channel formation region tends to have normally-on characteristics. Therefore, it is preferable to reduce the concentration of alkali metals or alkaline earth metals in the metal oxide. Specifically, the concentration of the alkali metal or alkaline earth metal in the metal oxide obtained by SIMS (concentration obtained by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry)) is 1×10 ¹⁸ atoms. /cm ³ or less, preferably 2×10 ¹⁶ atoms/cm ³ or less.

In addition, since hydrogen contained in the metal oxide reacts with oxygen bonded to the metal atom to become water, oxygen vacancies may be formed. When hydrogen enters the oxygen vacancies, electrons, which are carriers, are generated in some cases. In addition, part of hydrogen may bond with oxygen that bonds with a metal atom to generate an electron, which is a carrier. Therefore, a transistor using a metal oxide containing hydrogen tends to have normally-on characteristics.

Therefore, it is preferable that hydrogen in the metal oxide is reduced as much as possible. Specifically, in the metal oxide, the hydrogen concentration obtained by SIMS is less than 1×10 ²⁰ atoms/cm ³ , preferably less than 1×10 ¹⁹ atoms/cm ³ , more preferably less than 5×10 ¹⁸ atoms/cm Less than ³ , more preferably less than 1×10 ¹⁸ atoms/cm ³ . By using a metal oxide in which impurities are sufficiently reduced for a channel formation region of a transistor, stable electrical characteristics can be imparted.

A highly crystalline thin film is preferably used as a metal oxide used for a semiconductor of a transistor. By using the thin film, the stability or reliability of the transistor can be improved. The thin film includes, for example, a single-crystal metal oxide thin film or a polycrystalline metal oxide thin film. However, forming a single crystal metal oxide thin film or a polycrystalline metal oxide thin film on a substrate requires a high temperature or laser heating process. Therefore, the cost of the manufacturing process increases, and the throughput also decreases.

Non-Patent Document 1 and Non-Patent Document 2 report that an In--Ga--Zn oxide having a CAAC structure (referred to as CAAC-IGZO) was discovered in 2009. Here, it is reported that CAAC-IGZO has c-axis orientation, does not clearly identify grain boundaries, and can be formed on a substrate at low temperatures. Furthermore, it has been reported that transistors using CAAC-IGZO have excellent electrical characteristics and reliability.

In 2013, an In--Ga--Zn oxide having an nc structure (referred to as nc-IGZO) was discovered (see Non-Patent Document 3). Here, it is reported that nc-IGZO has periodicity in atomic arrangement in a minute region (for example, a region of 1 nm or more and 3 nm or less), and no regularity in crystal orientation is observed between different regions. there is

Non-Patent Document 4 and Non-Patent Document 5 show changes in the average crystal size due to electron beam irradiation of each of the thin films of CAAC-IGZO, nc-IGZO, and IGZO with low crystallinity. In thin films of IGZO with low crystallinity, crystalline IGZO of about 1 nm has been observed even before electron beam irradiation. Therefore, it is reported here that the presence of a completely amorphous structure could not be confirmed in IGZO. Furthermore, it has been shown that CAAC-IGZO thin films and nc-IGZO thin films have higher stability against electron beam irradiation than IGZO thin films with low crystallinity. Therefore, a thin film of CAAC-IGZO or a thin film of nc-IGZO is preferably used as a semiconductor of a transistor.

A transistor using a metal oxide has an extremely small leakage current in a non-conducting state. Specifically, an off current per 1 μm channel width of the transistor is on the order of yA/μm (10 ⁻²⁴ A/μm). is shown in Non-Patent Document 6. For example, a low-power-consumption CPU that utilizes the low leakage current characteristic of a transistor using a metal oxide has been disclosed (see Non-Patent Document 7).

In addition, application of a transistor using a metal oxide to a display device has been reported, taking advantage of the low leakage current characteristic of the transistor (see Non-Patent Document 8). In a display device, displayed images are switched several tens of times per second. The number of image switching times per second is called a refresh rate. Also, the refresh rate is sometimes called a drive frequency. Such high-speed screen switching, which is difficult for the human eye to perceive, is considered to be the cause of eye fatigue. Therefore, it has been proposed to reduce the number of times the image is rewritten by lowering the refresh rate of the display device. In addition, power consumption of the display device can be reduced by driving with a reduced refresh rate. Such a driving method is called idling stop (IDS) driving.

The discovery of CAAC and nc structures has contributed to improved electrical properties and reliability of transistors using metal oxides with CAAC or nc structures, as well as reduced cost and increased throughput of the manufacturing process. In addition, application research of the transistor to display devices and LSIs is underway, taking advantage of the characteristic of the transistor having a low leakage current.

<Method for manufacturing a semiconductor device>
Next, a method for manufacturing a semiconductor device having the transistor 200 according to the present invention, which is illustrated in FIG. 1, will be described with reference to FIGS. 3 to 9, (A) in each figure shows a top view. (B) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A1-A2 shown in (A), and is also a cross-sectional view of the transistor 200 in the channel length direction. (C) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A3-A4 in (A), and is also a cross-sectional view of the transistor 200 in the channel width direction. In addition, in the top view of (A) of each figure, some elements are omitted for clarity of illustration.

First, a substrate (not shown) is prepared, and an insulator 210 is formed on the substrate. The insulator 210 is formed by sputtering, chemical vapor deposition (CVD), molecular beam epitaxy (MBE), pulsed laser deposition (PLD), or ALD. (Atomic Layer Deposition) method or the like can be used.

The CVD method can be classified into a plasma enhanced CVD (PECVD) method using plasma, a thermal CVD (TCVD) method using heat, a photo CVD (Photo CVD) method using light, and the like. . Further, the method can be classified into a metal CVD (MCVD: Metal CVD) method and an organic metal CVD (MOCVD: Metal Organic CVD) method depending on the raw material gas used.

The plasma CVD method can obtain high quality films at relatively low temperatures. Moreover, since the thermal CVD method does not use plasma, it is a film formation method capable of reducing plasma damage to the object to be processed. For example, wiring, electrodes, elements (transistors, capacitive elements, etc.) included in a semiconductor device may be charged up by receiving charges from plasma. At this time, the accumulated charges may destroy wiring, electrodes, elements, and the like included in the semiconductor device. On the other hand, a thermal CVD method that does not use plasma does not cause such plasma damage, so that the yield of semiconductor devices can be increased. Moreover, since the thermal CVD method does not cause plasma damage during film formation, a film with few defects can be obtained.

In addition, the ALD method makes use of the self-limiting properties of atoms, allowing atoms to be deposited layer by layer. There are effects such as the ability to form a film with few defects such as holes, the ability to form a film with excellent coverage, and the ability to form a film at a low temperature. The ALD method also includes a PEALD (Plasma Enhanced ALD) method, which is a film forming method using plasma. By using plasma, film formation can be performed at a lower temperature, which is preferable in some cases. Some precursors used in the ALD method contain impurities such as carbon. Therefore, a film formed by the ALD method may contain more impurities such as carbon than films formed by other film formation methods. Note that quantification of impurities can be performed using X-ray photoelectron spectroscopy (XPS).

The CVD method and the ALD method are film forming methods in which a film is formed by a reaction on the surface of the object to be processed, unlike film forming methods in which particles emitted from a target or the like are deposited. Therefore, it is a film forming method which is not easily affected by the shape of the object to be processed and which has good step coverage. In particular, the ALD method has excellent step coverage and excellent thickness uniformity, and is therefore suitable for coating the surface of an opening with a high aspect ratio. However, since the ALD method has a relatively slow film formation rate, it may be preferable to use it in combination with another film formation method, such as the CVD method, which has a high film formation rate.

In the CVD method and the ALD method, the composition of the film obtained can be controlled by the flow rate ratio of the raw material gases. For example, in the CVD method and the ALD method, it is possible to form a film of any composition depending on the flow rate ratio of source gases. Further, for example, in the CVD method and the ALD method, it is possible to form a film whose composition is continuously changed by changing the flow rate ratio of the source gases while forming the film. When forming a film while changing the flow rate ratio of the raw material gases, the time required for film formation is reduced compared to film formation using multiple film formation chambers, as the time required for transportation and pressure adjustment is not required. can do. Therefore, productivity of semiconductor devices can be improved in some cases.

In this embodiment, the insulator 210 is formed using aluminum oxide by a sputtering method. Moreover, the insulator 210 may have a multilayer structure. For example, a structure in which an aluminum oxide film is formed by a sputtering method and an aluminum oxide film is formed on the aluminum oxide film by an ALD method may be employed. Alternatively, a structure may be employed in which aluminum oxide is deposited by an ALD method and aluminum oxide is deposited over the aluminum oxide by a sputtering method.

Next, a conductive film to be the conductor 203 is formed over the insulator 210 . A conductive film to be the conductor 203 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. Further, the conductive film to be the conductor 203 can be a multilayer film. In this embodiment mode, a tungsten film is formed as the conductive film to be the conductor 203 .

Next, the conductive film to be the conductor 203 is processed by lithography to form the conductor 203 .

In the lithography method, first, the resist is exposed through a mask. The exposed regions are then removed or left behind using a developer to form a resist mask. Next, a conductor, a semiconductor, an insulator, or the like can be processed into a desired shape by etching treatment through the resist mask. For example, a resist mask may be formed by exposing a resist using KrF excimer laser light, ArF excimer laser light, EUV (Extreme Ultraviolet) light, or the like. Alternatively, a liquid immersion technique may be used in which a liquid (for example, water) is filled between the substrate and the projection lens for exposure. Also, an electron beam or an ion beam may be used instead of the light described above. A mask is not necessary when using an electron beam or an ion beam. Note that the resist mask can be removed by dry etching treatment such as ashing, wet etching treatment, dry etching treatment followed by wet etching treatment, or wet etching treatment followed by dry etching treatment.

A hard mask made of an insulator or a conductor may be used instead of the resist mask. In the case of using a hard mask, an insulating film or a conductive film serving as a hard mask material is formed over the conductive film serving as the conductor 203, a resist mask is formed thereover, and the hard mask material is etched to obtain a desired shape. A hard mask can be formed. The etching of the conductive film to be the conductor 203 may be performed after removing the resist mask or may be performed with the resist mask left. In the latter case, the resist mask may disappear during etching. The hard mask may be removed by etching after the conductive film to be the conductor 203 is etched. On the other hand, if the hard mask material does not affect the post-process, or if it can be used in the post-process, it is not always necessary to remove the hard mask.

As a dry etching device, a capacitively coupled plasma (CCP) etching device having parallel plate electrodes can be used. A capacitively coupled plasma etching apparatus having parallel plate electrodes may be configured to apply a high frequency power supply to one of the parallel plate electrodes. Alternatively, a plurality of different high-frequency power sources may be applied to one of the parallel plate electrodes. Alternatively, a high-frequency power source of the same frequency may be applied to each parallel plate type electrode. Alternatively, a configuration in which high-frequency power sources with different frequencies are applied to the parallel plate electrodes may be used. Alternatively, a dry etching apparatus having a high density plasma source can be used. For example, an inductively coupled plasma (ICP) etching apparatus can be used as a dry etching apparatus having a high-density plasma source.

Next, an insulating film to be the insulator 212 is formed over the insulator 210 and the conductor 203 . The insulator to be the insulator 212 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. In this embodiment mode, the insulating film to be the insulator 212 is formed using silicon oxide by a CVD method.

Here, the thickness of the insulating film to be the insulator 212 is preferably greater than or equal to the thickness of the conductor 203 . For example, if the thickness of the conductor 203 is 1, the thickness of the insulating film to be the insulator 212 is 1 or more and 3 or less. In this embodiment mode, the thickness of the conductor 203 is set to 150 nm, and the thickness of the insulating film to be the insulator 212 is set to 350 nm.

Next, the insulating film to be the insulator 212 is subjected to CMP (chemical mechanical polishing) treatment to remove part of the insulating film to be the insulator 212 and expose the surface of the conductor 203 . Thus, the conductor 203 and the insulator 212 with flat top surfaces can be formed (see FIG. 3).

From here, a method of forming the conductor 203 different from the above will be described below.

An insulator 212 is deposited over the insulator 210 . The insulator 212 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Next, an opening is formed in the insulator 212 to reach the insulator 210 . The opening includes, for example, grooves and slits. Also, an area in which an opening is formed may be referred to as an opening. Wet etching may be used to form the openings, but dry etching is preferable for fine processing. For the insulator 210, it is preferable to select an insulator that functions as an etching stopper film when the insulator 212 is etched to form a groove. For example, when a silicon oxide film is used for the insulator 212 forming the trench, a silicon nitride film, an aluminum oxide film, or a hafnium oxide film is preferably used for the insulator 210 .

After forming the opening, a conductive film to be the conductor 203 is formed. The conductive film preferably contains a conductor having a function of suppressing permeation of oxygen. For example, tantalum nitride, tungsten nitride, titanium nitride, etc. can be used. Alternatively, a laminated film of tantalum, tungsten, titanium, molybdenum, aluminum, copper, and a molybdenum-tungsten alloy can be used. A conductive film to be the conductor 203 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

In this embodiment mode, the conductive film to be the conductor 203 has a multilayer structure. First, a tantalum nitride film is formed by a sputtering method, and titanium nitride is laminated on the tantalum nitride. By using such a metal nitride in the lower layer of the conductive film that serves as the conductor 203, even if a metal that is easily diffused, such as copper, is used as the upper layer of the conductive film that serves as the conductor 203, which will be described later, the metal can be used. can be prevented from diffusing out of the conductor 203 .

Next, a conductive film is formed as an upper layer of the conductive film to be the conductor 203 . The conductive film can be formed by a plating method, a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. In this embodiment mode, a low-resistance conductive material such as copper is deposited as a conductive film over the conductive film to be the conductor 203 .

Next, by performing CMP treatment, the upper layer of the conductive film to be the conductor 203 and part of the lower layer of the conductive film to be the conductor 203 are removed, and the insulator 212 is exposed. As a result, the conductive film that becomes the conductor 203 remains only in the opening. Thus, the conductor 203 with a flat upper surface can be formed. Note that part of the insulator 212 may be removed by the CMP treatment. The above is a different formation method of the conductor 203 .

Next, an insulator 214 is formed over the insulator 212 and the conductor 203 . The insulator 214 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. In this embodiment mode, a silicon nitride film is formed as the insulator 214 by a CVD method. In this way, by using an insulator such as silicon nitride through which copper is difficult to permeate as the insulator 214 , even if a metal such as copper which is easily diffused is used as the second conductor of the conductor 203 , the metal is insulated. Diffusion into layers above body 214 can be suppressed.

Next, an insulator 216 is formed over the insulator 214 . The insulator 216 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. In this embodiment, the insulator 216 is formed using silicon oxide by a CVD method.

Next, an opening reaching the conductor 203 is formed in the insulator 214 and the insulator 216 . A wet etching method may be used to form the opening, but it is preferable to use a dry etching method for fine processing.

After forming the opening, a conductive film to be the conductor 205a is formed. The conductive film to be the conductor 205a preferably contains a conductive material that has a function of suppressing permeation of oxygen. For example, tantalum nitride, tungsten nitride, titanium nitride, or the like can be used. Alternatively, a laminated film of tantalum, tungsten, titanium, molybdenum, aluminum, copper, and a molybdenum-tungsten alloy can be used. A conductive film to be the conductor 205a can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

In this embodiment mode, a tantalum nitride film is formed by a sputtering method as the conductive film to be the conductor 205a.

Next, a conductive film to be the conductor 205b is formed over the conductive film to be the conductor 205a. The conductive film can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

In this embodiment mode, as the conductive film to be the conductor 205b, a titanium nitride film is formed by a CVD method, and tungsten is formed over the titanium nitride film by a CVD method.

Next, by performing CMP treatment, the conductive film to be the conductor 205a and part of the conductive film to be the conductor 205b are removed, and the insulator 216 is exposed. As a result, the conductive film to be the conductor 205a and the conductive film to be the conductor 205b remain only in the opening. Thus, the conductor 205 including the conductor 205a and the conductor 205b with a flat top surface can be formed (see FIG. 3). Note that part of the insulator 216 is removed by the CMP treatment in some cases.

Next, an insulator 220 is formed over the insulator 216 and the conductor 205 . The insulator 220 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. In this embodiment, silicon oxide is deposited as the insulator 212 by a CVD method.

Next, an insulator 222 is formed over the insulator 220 . As the insulator 222, an insulator containing an oxide of one or both of aluminum and hafnium is preferably deposited. Note that as the insulator containing oxides of one or both of aluminum and hafnium, aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), or the like is preferably used. Insulators containing oxides of one or both of aluminum and hafnium have barrier properties against oxygen, hydrogen, and water. Since the insulator 222 has barrier properties against hydrogen and water, diffusion of hydrogen and water contained in structures provided around the transistor 200 into the transistor 200 through the insulator 222 is suppressed. , the generation of oxygen vacancies in the oxide 230 can be suppressed.

The insulator 222 can be deposited by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Next, an insulating film to be the insulator 224 is formed over the insulator 222 . An insulating film to be the insulator 224 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Subsequently, heat treatment is preferably performed. The heat treatment may be performed at 250° C. or higher and 650° C. or lower, preferably 300° C. or higher and 500° C. or lower, more preferably 320° C. or higher and 450° C. or lower. Note that the heat treatment is performed in a nitrogen or inert gas atmosphere, or an atmosphere containing an oxidizing gas of 10 ppm or more, 1% or more, or 10% or more. Moreover, you may perform heat processing in a pressure-reduced state. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas in order to compensate for desorbed oxygen after heat treatment in a nitrogen or inert gas atmosphere. good.

In this embodiment mode, heat treatment is performed at a temperature of 400° C. for 1 hour in a nitrogen atmosphere after the insulator 224 is formed. Impurities such as water and hydrogen contained in the insulator 224 can be removed by the heat treatment.

Alternatively, the heat treatment can be performed after the insulator 220 is deposited and after the insulator 222 is deposited. Although the above heat treatment conditions can be used for the heat treatment, the heat treatment after the insulator 220 is formed is preferably performed in an atmosphere containing nitrogen.

Here, in order to form an excess oxygen region in the insulator 224, plasma treatment containing oxygen may be performed under reduced pressure. For plasma treatment containing oxygen, it is preferable to use an apparatus having a power supply that generates high-density plasma using microwaves, for example. Alternatively, the board may have a power supply for applying RF (Radio Frequency). By using high-density plasma, high-density oxygen radicals can be generated, and by applying RF to the substrate side, the oxygen radicals generated by the high-density plasma can be efficiently guided into the insulator 224. can. Alternatively, plasma treatment containing an inert gas may be performed using this apparatus, and then plasma treatment containing oxygen may be performed to compensate for desorbed oxygen. Note that impurities such as water and hydrogen contained in the insulator 224 can be removed by appropriately selecting conditions for the plasma treatment. In that case, heat treatment may not be performed.

Next, an oxide film 230A to be the oxide 230a, an oxide film 230B to be the oxide 230b, and a conductive film 242A to be the conductor 242 are sequentially formed over the insulator 224 (see FIG. 3). Note that the oxide film is preferably formed continuously without being exposed to the atmospheric environment. By forming the films without exposure to the atmosphere, it is possible to prevent impurities or moisture from the atmospheric environment from adhering to the oxide films 230A and 230B. can be kept clean.

The oxide film 230A, the oxide film 230B, and the conductive film 242A can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

For example, when the oxide films 230A and 230B are formed by a sputtering method, oxygen or a mixed gas of oxygen and rare gas is used as the sputtering gas. By increasing the proportion of oxygen contained in the sputtering gas, excess oxygen in the formed oxide film can be increased. Further, when the above oxide film is formed by a sputtering method, the above In--M--Zn oxide target can be used.

In particular, part of oxygen contained in the sputtering gas may be supplied to the insulator 224 when forming the oxide film 230A. Therefore, the ratio of oxygen contained in the sputtering gas for the oxide film 230A should be 70% or more, preferably 80% or more, more preferably 100%.

In the case of forming the oxide film 230B by a sputtering method, if the oxygen content in the sputtering gas is 1% to 30%, preferably 5% to 20%, an oxygen-deficient oxide semiconductor is formed. It is formed. A transistor in which an oxygen-deficient oxide semiconductor is used for a channel formation region has relatively high field-effect mobility.

In this embodiment, the oxide film 230A is formed of In:Ga:Zn=1:1:0.5 [atomic ratio] (2:2:1 [atomic ratio]) or 1:3 by a sputtering method. : A film is formed using a target of 4 [atomic number ratio]. Also, the oxide film 230B is formed by a sputtering method using a target of In:Ga:Zn=4:2:4.1 [atomic ratio]. It should be noted that each oxide film may be formed in accordance with the characteristics required for the oxide 230 by appropriately selecting the film formation conditions and the atomic ratio.

Next, heat treatment may be performed. The heat treatment conditions described above can be used for the heat treatment. Impurities such as water and hydrogen in the oxide films 230A and 230B can be removed by heat treatment. In this embodiment mode, treatment is performed at a temperature of 400° C. for 1 hour in a nitrogen atmosphere, and then treatment is continuously performed at a temperature of 400° C. in an oxygen atmosphere for 1 hour.

Next, the oxide film 230A, the oxide film 230B and the conductive film 242A are processed into an island shape to form the oxide 230a, the oxide 230b and the conductive layer 242B. Note that in this step, the thickness of the region of the insulator 224 which does not overlap with the oxide 230a may be thin (see FIG. 4).

Here, the oxides 230 a and 230 b and the conductor layer 242 B are formed so that at least part of them overlaps with the conductor 205 . Moreover, the side surfaces of the oxides 230a, 230b, and the conductor layer 242B are preferably substantially perpendicular to the top surface of the insulator 222. FIG. The side surfaces of the oxides 230a and 230b, and the conductor layer 242B are substantially perpendicular to the top surface of the insulator 222, so that when a plurality of transistors 200 are provided, the area can be reduced and the density can be increased. Become. Alternatively, the oxide 230a, the oxide 230b, the conductor layer 242B, and the top surface of the insulator 222 may form a small angle. In that case, the angle between the side surfaces of the oxides 230a and 230b and the top surface of the insulator 222 is preferably 60° or more and less than 70°. With such a shape, the coverage with the insulator 273 or the like is improved in subsequent steps, and defects such as voids can be reduced.

Moreover, a curved surface is provided between the side surface of the conductor layer 242B and the upper surface of the conductor layer 242B. That is, it is preferable that the edge of the side surface and the edge of the upper surface are curved (hereinafter also referred to as a round shape). For example, the curved surface has a radius of curvature of 3 nm or more and 10 nm or less, preferably 5 nm or more and 6 nm or less, at the end of the conductor layer 242B. Since the edges do not have corners, the coverage of the film in the subsequent film forming process is improved.

Note that processing of the oxide film may be performed using a lithography method. A dry etching method or a wet etching method can be used for the processing. Processing by the dry etching method is suitable for fine processing.

Further, when dry etching or the like is performed, impurities caused by an etching gas or the like may adhere to or diffuse onto or inside the oxides 230a and 230b. Impurities include, for example, fluorine or chlorine.

Cleaning is performed to remove the above impurities. As a cleaning method, wet cleaning using a cleaning solution or the like, plasma treatment using plasma, cleaning by heat treatment, or the like may be used, and the above cleaning may be performed in combination as appropriate.

As wet cleaning, cleaning treatment may be performed using an aqueous solution obtained by diluting oxalic acid, phosphoric acid, hydrofluoric acid, or the like with carbonated water or pure water. Alternatively, ultrasonic cleaning using pure water or carbonated water may be performed. In this embodiment, ultrasonic cleaning is performed using pure water or carbonated water.

Subsequently, heat treatment may be performed. As the conditions for the heat treatment, the conditions for the heat treatment described above can be used.

Next, a dummy gate film to be dummy gate layer 262A is formed on insulator 224, oxide 230a, oxide 230b and conductor layer 242B.

A dummy gate film that becomes the dummy gate layer 262A is processed and used as a dummy gate. A dummy gate is a temporary gate electrode. That is, a temporary gate electrode is formed by processing a dummy gate film that will become the dummy gate layer 262A, the dummy gate is removed in a later step, and a gate electrode made of a conductive film or the like is formed instead. Therefore, it is preferable to use a film that can be easily microfabricated and easily removed as the dummy gate film that becomes the dummy gate layer 262A.

The formation of the dummy gate film to be the dummy gate layer 262A can be performed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. For example, insulators, semiconductors, or conductors can be used. Specifically, silicon such as polysilicon, microcrystalline silicon, and amorphous silicon, and metal films such as aluminum, titanium, and tungsten may be used. Alternatively, a coating method may be used to form SOG (Spin On Glass), a resin film, or the like. Examples include photoresists, polyesters, polyolefins, polyamides (nylons, aramids, etc.), polyimides, polycarbonates or acrylics. The surface of the dummy gate film can be flattened by forming the SOG and resin film by a coating method. By flattening the surface of the dummy gate film in this manner, microfabrication is facilitated, and removal is also facilitated.

Also, the dummy gate film to be the dummy gate layer 262A can be a multi-layered film using different film types. For example, a dummy gate film to be the dummy gate layer 262A can be a two-layer film in which a conductive film and a resin film are formed over the conductive film. By making the dummy gate film have such a structure, the conductive film may function as a stopper film for the CMP process in a later CMP process, for example. Alternatively, it may be possible to detect the end point of the CMP processing, and it may be possible to reduce processing variations.

Next, the dummy gate film to be the dummy gate layer 262A is etched by lithography to form the dummy gate layer 262A (see FIG. 5). Dummy gate layer 262 A is formed to at least partially overlap conductor 205 and oxide 230 .

Next, an insulating film 254A is formed to cover the oxide 230a, the oxide 230b, the conductor layer 242B and the dummy gate layer 262A. Subsequently, an insulating film 255A may be formed over the insulating film 254A (see FIG. 5). The insulating film 254A and the insulating film 255A can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

An insulating film having a function of suppressing permeation of oxygen is preferably used for the insulating film 254A. For example, it is preferable to form an aluminum oxide film by a sputtering method. By forming an aluminum oxide film using a gas containing oxygen by a sputtering method, oxygen can be injected into the insulator 224 . That is, the insulator 224 can have excess oxygen.

An insulating film having a function of suppressing permeation of oxygen is preferably used for the insulating film 255A. For example, it is preferable to form an aluminum oxide film by ALD. By using the ALD method with excellent coverage, it is possible to form the insulating film 255A having a uniform thickness even in the stepped portion formed by the dummy gate layer 262A or the like. Also, by using the ALD method, a dense thin film can be formed. Since a dense thin film with excellent coverage can be formed, even if defects such as voids or pinholes occur in the insulating film 254A, they can be covered with the insulating film 255A.

As described above, excess oxygen contained in the insulator 224 can be prevented from diffusing outward, and impurities such as water and hydrogen can be prevented from entering the insulator 224 from the outside. Note that the formation of the insulating film 255A can be omitted.

Next, an insulating film to be the insulator 280 is formed over the insulating film 255A. An insulating film to be the insulator 280 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Next, the insulator 280, the dummy gate layer 262A, the insulator 254A, and the insulator 255A are partly removed until part of the dummy gate layer 262A is exposed. An insulator 254 and an insulator 255 are formed (see FIG. 6). A CMP process is preferably used to form insulator 280 , dummy gate 262 , insulator 254 and insulator 255 .

Further, as described above, by forming the dummy gate layer 262A as a film having a two-layer structure in which, for example, a conductive film and a resin film are formed on the conductive film, the conductive film serves as a stopper film for the CMP process in the CMP process. may function as Alternatively, the conductive film may be able to detect the end point of the CMP process, and it may be possible to reduce variations in the height of the dummy gate 262 . As shown in FIG. 6A, the top surface of the dummy gate 262 and the top surfaces of the insulators 254, 255, and 280 are substantially aligned.

Next, dummy gate 262 is removed. Removal of the dummy gate 262 can be performed using wet etching, dry etching, ashing, or the like. Alternatively, a plurality of the above processes may be combined as appropriate. For example, wet etching may be performed after ashing. By removing dummy gate 262, a portion of the surface of conductive layer 242B is exposed.

Exposed portions of conductor layer 242B may then be removed to expose portions of the surface of oxide 230b, forming conductors 242a and 242b. The removal can be performed using wet etching or dry etching. Dry etching is used in this embodiment mode. It is preferable to use dry etching because fine processing can be performed.

Next, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used, but the heat treatment may be performed under reduced pressure and the oxide film 230C may be continuously formed without exposure to the atmosphere. By such treatment, moisture and hydrogen adsorbed to the surface of the oxide 230b or the like can be removed, and the moisture concentration and hydrogen concentration in the oxide 230a and the oxide 230b can be reduced. .

The oxide film 230C can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. An oxide film to be the oxide film 230C may be formed using a film formation method similar to that for the oxide film 230A or the oxide film 230B in accordance with the characteristics required for the oxide film 230C. In this embodiment, a target of In:Ga:Zn=1:3:4 [atomic ratio] or 4:2:4.1 [atomic ratio] is used as the oxide film 230C by a sputtering method. form a film.

In particular, part of the oxygen contained in the sputtering gas may be supplied to the oxides 230a and 230b when forming the oxide film 230C. Therefore, the ratio of oxygen contained in the sputtering gas for the oxide film 230C should be 70% or more, preferably 80% or more, and more preferably 100%.

Next, an insulating film 250A is formed. The insulating film 250A can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As the insulating film 250A, silicon oxynitride is preferably deposited by a CVD method. The film formation temperature for forming the insulating film 250A is preferably 350.degree. C. or more and less than 450.degree. By forming the insulating film 250A at 400° C., an insulator with few impurities can be formed.

Note that oxygen can be introduced into the insulating film 250A by exciting oxygen with microwaves to generate high-density oxygen plasma and exposing the insulating film 250A to the oxygen plasma.

Alternatively, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used. By the heat treatment, the moisture concentration and the hydrogen concentration of the insulating film 250A can be reduced.

Next, a conductive film 260Aa and a conductive film 260Ab are formed. The conductive films 260Aa and 260Ab can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. For example, it is preferable to use the CVD method. In this embodiment mode, the conductive film 260Aa is formed using the ALD method, and the conductive film 260Ab is formed using the CVD method (see FIG. 7).

Next, the oxide film 230C, the insulating film 250A, the conductive film 260Aa, and the conductive film 260Ab are polished by CMP treatment until the insulator 280 is exposed, thereby polishing the oxide film 230c, the insulator 250, and the conductor 260 (the conductor 260a). and conductors 260b) are formed (see FIG. 8).

Next, an insulating film to be the insulator 274 may be formed over the insulator 280 . An insulating film to be the insulator 274 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As the insulating film to be the insulator 274, for example, an aluminum oxide film is preferably formed by a sputtering method. By forming an aluminum oxide film by a sputtering method, diffusion of hydrogen in the insulator 280 to the oxide 230 can be suppressed in some cases (see FIG. 8).

Next, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used. By the heat treatment, the moisture concentration and the hydrogen concentration of the insulator 280 can be reduced.

Next, an insulator to be the insulator 281 may be formed over the insulator 274 . An insulating film to be the insulator 281 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like (see FIG. 8).

Next, openings are formed in the insulators 254, 255, 280, 274, and 281 to reach the conductors 242a and 242b. The formation of the opening may be performed using a lithography method.

Next, an insulating film to be the insulator 241 is formed, and the insulating film is anisotropically etched to form the insulator 241 . The conductive film can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As an insulating film to be the insulator 241, an insulating film having a function of suppressing permeation of oxygen is preferably used. For example, it is preferable to form an aluminum oxide film by ALD. Moreover, the anisotropic etching may be performed by, for example, a dry etching method. By configuring the side walls of the opening in such a manner, permeation of oxygen from the outside can be suppressed, and oxidation of the conductors 240a and 240b to be formed next can be prevented. Further, impurities such as water and hydrogen can be prevented from diffusing to the outside from the conductors 240a and 240b.

Next, a conductive film to be the conductor 240a and the conductor 240b is formed. The conductive films to be the conductors 240a and 240b preferably have a stacked-layer structure including a conductor that has a function of suppressing permeation of impurities such as water and hydrogen. For example, a laminate of tantalum nitride, titanium nitride, etc., and tungsten, molybdenum, copper, etc., can be used. A conductive film to be the conductor 240 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Next, CMP treatment is performed to remove part of the conductive film to be the conductors 240 a and 240 b to expose the insulator 281 . As a result, the conductor 240a and the conductor 240b with flat top surfaces can be formed by leaving the conductive film only in the openings (see FIG. 1). Note that part of the insulator 281 is removed by the CMP treatment in some cases.

Through the above steps, a semiconductor device including the transistor 200 illustrated in FIG. 1 can be manufactured. As illustrated in FIGS. 3A to 9B, the transistor 200 can be manufactured by using the method for manufacturing the semiconductor device described in this embodiment.

According to one embodiment of the present invention, a semiconductor device with high on-state current can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with high frequency characteristics can be provided. Alternatively, according to one embodiment of the present invention, a highly reliable semiconductor device can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device that can be miniaturized or highly integrated can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with favorable electrical characteristics can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with low off-state current can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with low power consumption can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with high productivity can be provided.

The structures, methods, and the like described in this embodiment can be combined as appropriate with the structures, methods, and the like described in other embodiments.

<Modified Example of Semiconductor Device>
An example of a semiconductor device including the transistor 200 according to one embodiment of the present invention, which is different from the semiconductor device described in <Structure Example of Semiconductor Device>, will be described below with reference to FIGS.

Moreover, (A) of each figure shows a top view. (B) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A1-A2 shown in (A), and is also a cross-sectional view of the transistor 200 in the channel length direction. (C) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A3-A4 in (A), and is also a cross-sectional view of the transistor 200 in the channel width direction. In the top view of (A) of each figure, some elements are omitted for clarity of illustration.

In the semiconductor devices shown in FIGS. 9 and 15, structures having the same functions as structures constituting the semiconductor device (see FIG. 1) shown in <Structure Example of Semiconductor Device> are denoted by the same reference numerals. . Note that in this item, the material described in detail in <Structure Example of Semiconductor Device> can be used as the material for forming the transistor 200 .

The semiconductor device shown in FIG. 9 differs from the semiconductor device shown in FIG. 1 in that it does not have the insulator 244 . Further, in the semiconductor device illustrated in FIG. 1, the insulator 254 and the insulator 255 are arranged between the oxide 230c and the insulator 280, and the oxide 230c and the insulator 280 are not in contact with each other. However, the semiconductor device shown in FIG. 9 differs from the semiconductor device shown in FIG. 1 in that the oxide 230c and the insulator 280 are in contact with each other.

The semiconductor device shown in FIG. 9 can be manufactured without forming the dummy gate 262, which is preferable because the manufacturing process of the semiconductor device can be simplified. For other structures and effects, the description of the semiconductor device illustrated in FIG. 1 can be referred to.

A method for manufacturing the semiconductor device illustrated in FIG. 9 is described below with reference to FIGS. (A) of each figure shows a top view. (B) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A1-A2 shown in (A), and is also a cross-sectional view of the transistor 200 in the channel length direction. (C) of each figure is a cross-sectional view corresponding to the portion indicated by the dashed-dotted line A3-A4 in FIG. In the top view of (A) of each figure, some elements are omitted for clarity of illustration.

The method for manufacturing the semiconductor device shown in FIG. 1 is the same as the method for manufacturing the semiconductor device shown in FIG. 1 up to the formation of the oxide 230a, the oxide 230b, and the conductor layer 242B (see FIG. 4).

Next, an insulating film 254A is formed over the insulator 224, the oxides 230a and 230b, and the conductor layer 242B (see FIG. 10).

An insulating film having a function of suppressing permeation of oxygen is preferably used for the insulating film 254A. For example, it is preferable to form an aluminum oxide film by a sputtering method. By forming an aluminum oxide film using a gas containing oxygen by a sputtering method, oxygen can be injected into the insulator 224 . That is, the insulator 224 can have excess oxygen.

Next, an insulating film to be the insulator 280 is formed over the insulating film 254A. An insulating film to be the insulator 280 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. Next, the insulating film to be the insulator 280 is subjected to CMP treatment to form the insulator 280 with a flat upper surface (see FIG. 10).

A portion of insulator 280, a portion of insulating film 254A, and a portion of conductive layer 242B are then processed to form an opening that reaches oxide 230b. The opening is preferably formed so as to overlap the conductors 203 and 205 . The openings form a conductor 242a, a conductor 242b, and an insulator 254 (see FIG. 11).

In addition, part of the insulator 280, part of the insulating film 254A, and part of the conductor may be processed under different conditions. For example, part of the insulator 280 may be processed by a dry etching method, part of the insulating film 254A may be processed by a wet etching method, and part of the conductor layer 242B may be processed by a dry etching method.

Next, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used, but the heat treatment may be performed under reduced pressure and the oxide film 230C may be continuously formed without exposure to the atmosphere. By such treatment, moisture and hydrogen adsorbed to the surface of the oxide 230b or the like can be removed, and the moisture concentration and hydrogen concentration in the oxide 230a and the oxide 230b can be reduced. .

The oxide film 230C can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. An oxide film to be the oxide film 230C may be formed using a film formation method similar to that for the oxide film 230A or the oxide film 230B in accordance with the characteristics required for the oxide film 230C. In this embodiment, a target of In:Ga:Zn=1:3:4 [atomic ratio] or 4:2:4.1 [atomic ratio] is used as the oxide film 230C by a sputtering method. form a film.

In particular, part of the oxygen contained in the sputtering gas may be supplied to the oxides 230a and 230b when forming the oxide film 230C. Therefore, the ratio of oxygen contained in the sputtering gas for the oxide film 230C should be 70% or more, preferably 80% or more, and more preferably 100%.

Next, an insulating film 250A is formed. The insulating film 250A can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As the insulating film 250A, silicon oxynitride is preferably deposited by a CVD method. The film formation temperature for forming the insulating film 250A is preferably 350.degree. C. or more and less than 450.degree. By forming the insulating film 250A at 400° C., an insulator with few impurities can be formed.

Note that oxygen can be introduced into the insulating film 250A by exciting oxygen with microwaves to generate high-density oxygen plasma and exposing the insulating film 250A to the oxygen plasma.

Alternatively, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used. By the heat treatment, the moisture concentration and the hydrogen concentration of the insulating film 250A can be reduced.

Next, a conductive film 260Aa and a conductive film 260Ab are formed. The conductive films 260Aa and 260Ab can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. For example, it is preferable to use the CVD method. In this embodiment mode, the conductive film 260Aa is formed using the ALD method, and the conductive film 260Ab is formed using the CVD method (see FIG. 12).

Next, the oxide film 230C, the insulating film 250A, the conductive film 260Aa, and the conductive film 260Ab are polished by CMP treatment until the insulator 280 is exposed, thereby polishing the oxide film 230c, the insulator 250, and the conductor 260 (the conductor 260a). and conductors 260b) are formed (see FIG. 13).

Next, an insulating film to be the insulator 274 may be formed over the insulator 280 . An insulating film to be the insulator 274 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As the insulating film to be the insulator 274, for example, an aluminum oxide film is preferably formed by a sputtering method. By forming an aluminum oxide film by a sputtering method, diffusion of hydrogen in the insulator 280 to the oxide 230 can be suppressed in some cases (see FIG. 13).

Next, heat treatment may be performed. For the heat treatment, the heat treatment conditions described above can be used. By the heat treatment, the moisture concentration and the hydrogen concentration of the insulator 280 can be reduced.

Next, an insulator to be the insulator 281 may be formed over the insulator 274 . The insulating film to be the insulator 281 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like (see FIG. 13).

Next, openings are formed in the insulators 254, 255, 280, 274, and 281 to reach the conductors 242a and 242b. The formation of the opening may be performed using a lithography method.

Next, an insulating film to be the insulator 241 is formed, and the insulating film is anisotropically etched to form the insulator 241 . The conductive film can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. As an insulating film to be the insulator 241, an insulating film having a function of suppressing permeation of oxygen is preferably used. For example, it is preferable to form an aluminum oxide film by ALD. Moreover, the anisotropic etching may be performed by, for example, a dry etching method. By configuring the side walls of the opening in such a manner, permeation of oxygen from the outside can be suppressed, and oxidation of the conductors 240a and 240b to be formed next can be prevented. Further, impurities such as water and hydrogen can be prevented from diffusing to the outside from the conductors 240a and 240b.

Next, a conductive film to be the conductor 240a and the conductor 240b is formed. The conductive films to be the conductors 240a and 240b preferably have a stacked-layer structure including a conductor that has a function of suppressing permeation of impurities such as water and hydrogen. For example, a laminate of tantalum nitride, titanium nitride, etc., and tungsten, molybdenum, copper, etc., can be used. A conductive film to be the conductor 240 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

Next, CMP treatment is performed to remove part of the conductive film to be the conductors 240 a and 240 b to expose the insulator 281 . As a result, the conductor 240a and the conductor 240b with flat top surfaces can be formed by leaving the conductive film only in the openings (see FIG. 9). Note that part of the insulator 281 is removed by the CMP treatment in some cases.

Through the above steps, a semiconductor device including the transistor 200 illustrated in FIG. 9 can be manufactured.

The transistor 200 shown in FIG. 14 is different from the transistor 200 shown in FIG. 1 in that the conductor 242 is not provided. In the transistor 200 illustrated in FIG. 14, for example, the regions 243 (the regions 243a and 243b) are formed by adding an element as a dopant that can increase the carrier density of the oxide 230 and reduce the resistance. Just do it.

As the dopant, an element that forms oxygen vacancies, an element that bonds with oxygen vacancies, or the like may be used. Such elements typically include boron or phosphorus. Alternatively, hydrogen, carbon, nitrogen, fluorine, sulfur, chlorine, titanium, rare gas, or the like may be used. Representative examples of rare gas elements include helium, neon, argon, krypton, and xenon. Metals such as aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, and lanthanum. Any one or more metal elements selected from the elements may be added. Among the above-mentioned dopants, boron and phosphorus are preferred. When boron or phosphorus is used as a dopant, it is possible to use equipment on a manufacturing line for amorphous silicon or low-temperature polysilicon, so equipment investment can be suppressed. The concentrations of the above elements may be measured using SIMS or the like.

In particular, it is preferable to use an element that easily forms an oxide as the element added to the region 243 . Such elements typically include boron, phosphorus, aluminum, magnesium, and the like. The element added to the region 243 can remove oxygen from the oxide 230 to form an oxide. As a result, many oxygen vacancies occur in the region 243 . The oxygen vacancies are combined with hydrogen in the oxide 230 to generate carriers and form a region with extremely low resistance. Furthermore, since the element added to the region 243 exists in the region 243 in the state of a stable oxide, it is difficult to desorb from the region 243 even if a treatment requiring a high temperature is performed in a subsequent step. That is, by using an element that easily forms an oxide as an element to be added to the region 243, a region that is unlikely to have a high resistance can be formed in the oxide 230 even through a high-temperature process.

By forming the region 243 functioning as a source region or a drain region in the oxide 230, the conductor 240 functioning as a plug can be connected to the region 243 without providing a source electrode and a drain electrode formed of metal. can.

In the case of forming the region 243 by adding a dopant, for example, a mask such as a resist mask or a hard mask may be provided at a position where the channel formation region of the transistor 200 is to be added, and the dopant is added. Thus, a region 243 containing the above element can be formed in a region of the oxide 230 which is not overlapped with the mask.

As a dopant addition method, an ion implantation method in which an ionized raw material gas is added after mass separation, an ion doping method in which an ionized raw material gas is added without mass separation, a plasma immersion ion implantation method, or the like can be used. can be done. When performing mass separation, the ion species to be added and their concentration can be strictly controlled. On the other hand, when mass separation is not performed, high-concentration ions can be added in a short time. Also, an ion doping method may be used in which clusters of atoms or molecules are generated and ionized. Note that the dopant may be replaced with an ion, a donor, an acceptor, an impurity, an element, or the like.

Further, by adding an element that forms oxygen vacancies to the region 243 and performing heat treatment, hydrogen contained in the region 234 functioning as a channel formation region can be captured by the oxygen vacancies contained in the region 243 in some cases. Accordingly, the transistor 200 can have stable electrical characteristics and can be improved in reliability.

The structures, structures, methods, and the like described in this embodiment can be used in appropriate combination with the structures, structures, methods, and the like described in other embodiments.

(Embodiment 2)
In this embodiment, one mode of a semiconductor device will be described with reference to FIGS.

[Storage device 1]
FIG. 15 illustrates an example of a semiconductor device (memory device) using a capacitor that is one embodiment of the present invention. In the semiconductor device of one embodiment of the present invention, the transistor 200 is provided above the transistor 300 and the capacitor 100 is provided above the transistors 300 and 200 . Note that the transistor 200 described in the above embodiment can be used as the transistor 200 .

The transistor 200 is a transistor whose channel is formed in a semiconductor layer including an oxide semiconductor. Since the transistor 200 has a low off-state current, when it is used for a memory device, stored data can be retained for a long time. That is, since the refresh operation is not required or the frequency of the refresh operation is extremely low, the power consumption of the memory device can be sufficiently reduced.

In the semiconductor device shown in FIG. 15 , a wiring 1001 is electrically connected to the source of the transistor 300 and a wiring 1002 is electrically connected to the drain of the transistor 300 . A wiring 1003 is electrically connected to one of the source and the drain of the transistor 200, a wiring 1004 is electrically connected to the first gate of the transistor 200, and a wiring 1006 is electrically connected to the second gate of the transistor 200. It is connected to the. The gate of the transistor 300 and the other of the source and drain of the transistor 200 are electrically connected to one electrode of the capacitor 100, and the wiring 1005 is electrically connected to the other electrode of the capacitor 100. .

Further, the memory device illustrated in FIG. 15 can form a memory cell array by being arranged in a matrix.

<Transistor 300>
The transistor 300 is provided on a substrate 311 and includes a conductor 316 functioning as a gate electrode, an insulator 315 functioning as a gate insulator, a semiconductor region 313 consisting of part of the substrate 311, and functioning as a source or drain region. It has a low resistance region 314a and a low resistance region 314b. Transistor 300 can be either p-channel or n-channel.

Here, in the transistor 300 shown in FIG. 15, the semiconductor region 313 (part of the substrate 311) in which the channel is formed has a convex shape. A conductor 316 is provided to cover the side and top surfaces of the semiconductor region 313 with an insulator 315 interposed therebetween. Note that the conductor 316 may be made of a material that adjusts the work function. Such a transistor 300 is also called a FIN transistor because it utilizes the projections of the semiconductor substrate. Note that an insulator that functions as a mask for forming the protrusion may be provided in contact with the upper portion of the protrusion. Further, here, the case where a part of the semiconductor substrate is processed to form a convex portion is shown, but a semiconductor film having a convex shape may be formed by processing an SOI substrate.

Note that the transistor 300 illustrated in FIG. 15 is only an example, and the structure thereof is not limited, and an appropriate transistor may be used depending on the circuit configuration and the driving method.

<Capacitor 100>
The capacitor 100 is provided above the transistor 200 . The capacitor 100 has a conductor 110 functioning as a first electrode, a conductor 120 functioning as a second electrode, and an insulator 130 functioning as a dielectric.

Further, for example, the conductor 112 provided over the conductor 246 and the conductor 110 can be formed at the same time. Note that the conductor 112 functions as a plug or a wiring electrically connected to the capacitor 100 , the transistor 200 , or the transistor 300 .

Although the conductors 112 and 110 have a single-layer structure in FIGS. 15A and 15B, they are not limited to this structure and may have a stacked structure of two or more layers. For example, between a conductor with a barrier property and a conductor with high conductivity, a conductor with a barrier property and a conductor with high adhesion to the conductor with high conductivity may be formed.

The insulator 130 is, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, hafnium oxide, hafnium oxynitride, hafnium nitride oxide, or hafnium nitride. etc., and can be provided as a laminate or a single layer.

For example, the insulator 130 preferably has a layered structure of a material with high dielectric strength such as silicon oxynitride and a high dielectric constant (high-k) material. With this configuration, the capacitive element 100 includes an insulator with a high dielectric constant (high-k), so that a sufficient capacitance can be secured, and an insulator with a high dielectric strength improves the dielectric strength and increases the capacitance. Electrostatic breakdown of the element 100 can be suppressed.

Note that insulators of high dielectric constant (high-k) materials (high dielectric constant materials) include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, and oxynitrides containing aluminum and hafnium. , oxides with silicon and hafnium, oxynitrides with silicon and hafnium, or nitrides with silicon and hafnium.

On the other hand, materials with high dielectric strength (materials with low dielectric constant) include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, fluorine-added silicon oxide, carbon-added silicon oxide, carbon, and nitrogen. There are doped silicon oxide, silicon oxide with vacancies, resin, and the like.

<Wiring layer>
A wiring layer provided with an interlayer film, a wiring, a plug, and the like may be provided between the structures. Also, the wiring layer can be provided in a plurality of layers depending on the design. Here, for conductors that function as plugs or wiring, a plurality of structures may be grouped together and given the same reference numerals. Further, in this specification and the like, the wiring and the plug electrically connected to the wiring may be integrated. That is, there are cases where a part of the conductor functions as a wiring and a part of the conductor functions as a plug.

For example, an insulator 320 , an insulator 322 , an insulator 324 , and an insulator 326 are stacked in this order over the transistor 300 as interlayer films. In addition, conductors 328, 330, and the like electrically connected to the capacitor 100 or the transistor 200 are embedded in the insulators 320, 322, 324, and 326, respectively. Note that the conductors 328 and 330 function as plugs or wirings.

Moreover, the insulator functioning as an interlayer film may function as a planarization film covering the uneven shape thereunder. For example, the top surface of the insulator 322 may be planarized by a chemical mechanical polishing (CMP) method or the like to improve planarity.

A wiring layer may be provided over the insulator 326 and the conductor 330 . For example, in FIG. 15, an insulator 350, an insulator 352, and an insulator 354 are stacked in this order. A conductor 356 is formed over the insulators 350 , 352 , and 354 . Conductor 356 functions as a plug or wiring.

Similarly, the insulator 210 , the insulator 212 , the insulator 214 , and the insulator 216 are embedded with a conductor 218 , a conductor forming the transistor 200 (the conductor 205 ), and the like. Note that the conductor 218 functions as a plug or wiring that is electrically connected to the capacitor 100 or the transistor 300 . Further, an insulator 150 is provided over the conductor 120 and the insulator 130 .

Insulators that can be used as the interlayer film include insulating oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, metal nitride oxides, and the like.

For example, by using a material with a low dielectric constant as an insulator functioning as an interlayer film, the parasitic capacitance generated between wirings can be reduced. Therefore, the material should be selected according to the function of the insulator.

For example, the insulator 150, the insulator 212, the insulator 352, the insulator 354, and the like preferably have an insulator with a low dielectric constant. For example, the insulator includes silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, and silicon oxide with vacancies. Alternatively, it is preferable to have a resin or the like. Alternatively, the insulator is silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide to which fluorine is added, silicon oxide to which carbon is added, silicon oxide to which carbon and nitrogen are added, or silicon oxide having vacancies. and resin. Since silicon oxide and silicon oxynitride are thermally stable, by combining them with a resin, a laminated structure that is thermally stable and has a low dielectric constant can be obtained. Examples of resin include polyester, polyolefin, polyamide (nylon, aramid, etc.), polyimide, polycarbonate, acrylic, and the like.

In addition, when a transistor including an oxide semiconductor is surrounded by an insulator having a function of suppressing permeation of impurities such as hydrogen and oxygen, electrical characteristics of the transistor can be stabilized. Therefore, an insulator having a function of suppressing permeation of impurities such as hydrogen and oxygen may be used for the insulator 210, the insulator 350, and the like.

Examples of insulators having a function of suppressing permeation of impurities such as hydrogen and oxygen include boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, and zirconium. Insulators including lanthanum, neodymium, hafnium, or tantalum may be used in single layers or stacks. Specifically, as an insulator having a function of suppressing permeation of impurities such as hydrogen and oxygen, aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, or A metal oxide such as tantalum oxide, silicon nitride oxide, silicon nitride, or the like can be used.

Conductors that can be used for wiring and plugs include aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, and indium. , ruthenium and the like can be used. Alternatively, a semiconductor with high electrical conductivity, typified by polycrystalline silicon containing an impurity element such as phosphorus, or a silicide such as nickel silicide may be used.

For example, the conductor 328, the conductor 330, the conductor 356, the conductor 218, the conductor 112, and the like are metal materials, alloy materials, metal nitride materials, metal oxide materials, or the like formed of any of the above materials. of conductive materials can be used in a single layer or in lamination. It is preferable to use a high-melting-point material such as tungsten or molybdenum that has both heat resistance and conductivity, and it is preferable to use tungsten. Alternatively, it is preferably made of a low-resistance conductive material such as aluminum or copper. Wiring resistance can be reduced by using a low-resistance conductive material.

<<Wiring or Plug in Layer Provided with Oxide Semiconductor>>
Note that when an oxide semiconductor is used for the transistor 200, an insulator having an excess oxygen region is provided near the oxide semiconductor in some cases. In that case, an insulator having a barrier property is preferably provided between the insulator having the excess oxygen region and the conductor provided in the insulator having the excess oxygen region.

For example, in FIG. 15, insulator 276 may be provided between insulator 224 and conductor 246 . In particular, the conductor 246 is preferably provided in contact with the insulator 222 sandwiching the insulator 224 having the excess oxygen region, the insulator 254 and the insulator 244 . By providing the insulator 276, the insulator 222, and the insulator 281 in contact with each other, the insulator 224 and the transistor 200 can be sealed with an insulator having a barrier property. Further, insulator 276 preferably contacts a portion of insulator 280 as well. By extending the insulator 276 to the insulator 280, diffusion of oxygen and impurities can be further suppressed.

In other words, the provision of the insulator 276 can prevent excess oxygen in the insulator 224 from being absorbed by the conductor 246 . In addition, with the insulator 276 , hydrogen, which is an impurity, can be prevented from diffusing into the transistor 200 through the conductor 246 .

Note that an insulating material having a function of suppressing diffusion of impurities such as water or hydrogen and oxygen is preferably used as the insulator 276 . For example, it is preferable to use aluminum oxide or hafnium oxide. In addition, metal oxides such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, or tantalum oxide, silicon nitride oxide, or silicon nitride can also be used.

The above is the description of the configuration example. With this structure, variation in electrical characteristics can be suppressed and reliability can be improved in a semiconductor device including a transistor including an oxide semiconductor. Alternatively, a transistor including an oxide semiconductor with high on-state current can be provided. Alternatively, a transistor including an oxide semiconductor with low off-state current can be provided. Alternatively, a semiconductor device with reduced power consumption can be provided.

[Storage device 2]
An example of a memory device using a semiconductor device of one embodiment of the present invention is shown in FIG. The memory device illustrated in FIG. 16 includes a transistor 400 in addition to the semiconductor device including the transistor 200, the transistor 300, and the capacitor 100 illustrated in FIG.

Transistor 400 can control the second gate voltage of transistor 200 . For example, the first gate and the second gate of the transistor 400 are diode-connected to the source, and the source of the transistor 400 and the second gate of the transistor 200 are connected. When the second gate of transistor 200 is held at a negative potential in this configuration, the first gate-source voltage and the second gate-source voltage of transistor 400 are 0V. Since the drain current of the transistor 400 is very small when the second gate voltage and the first gate voltage are 0 V, the second gate of the transistor 200 can be operated without supplying power to the transistors 200 and 400 . A negative potential can be maintained for a long time. Accordingly, the memory device including the transistors 200 and 400 can retain memory contents for a long period of time.

Therefore, the wiring 1001 is electrically connected to the source of the transistor 300 and the wiring 1002 is electrically connected to the drain of the transistor 300 in FIG. A wiring 1003 is electrically connected to one of the source and the drain of the transistor 200, a wiring 1004 is electrically connected to the gate of the transistor 200, and a wiring 1006 is electrically connected to the back gate of the transistor 200. . The gate of the transistor 300 and the other of the source and drain of the transistor 200 are electrically connected to one electrode of the capacitor 100, and the wiring 1005 is electrically connected to the other electrode of the capacitor 100. . A wiring 1007 is electrically connected to the source of the transistor 400, a wiring 1008 is electrically connected to the gate of the transistor 400, a wiring 1009 is electrically connected to the back gate of the transistor 400, and a wiring 1010 is the drain of the transistor 400. is electrically connected to Here, the wiring 1006, the wiring 1007, the wiring 1008, and the wiring 1009 are electrically connected.

Further, the memory device shown in FIG. 16 can form a memory cell array by arranging the memory devices in a matrix like the memory device shown in FIG. Note that one transistor 400 can control the second gate voltages of a plurality of transistors 200 . Therefore, the number of transistors 400 is preferably less than that of the transistors 200 .

<Transistor 400>
The transistor 400 is formed in the same layer as the transistor 200 and can be manufactured in parallel. The transistor 400 includes a conductor 460 (a conductor 460a and a conductor 460b) functioning as a first gate electrode, a conductor 405 (a conductor 405a and a conductor 405b) functioning as a second gate electrode, The insulator 220, the insulator 222, the insulator 224, and the insulator 450 functioning as gate insulating layers, an oxide 430c having a region where a channel is formed, a conductor 442a functioning as one of a source or a drain, and an oxide and an oxide 431b, a conductor 442b functioning as the other of the source and the drain, the oxide 432a and the oxide 432b, and the conductor 440 (the conductor 440a and the conductor 440b).

In transistor 400 , conductor 405 is in the same layer as conductor 205 . The oxides 431a and 432a and the oxide 230a are in the same layer, and the oxides 431b and 432b and the oxide 230b are in the same layer. Conductor 442 is the same layer as conductor 242 . Oxide 430c and oxide 230c are the same layer. Insulator 450 is the same layer as insulator 250 . Conductor 460 is the same layer as conductor 260 .

Note that structures formed in the same layer can be formed at the same time. For example, the oxide 430c can be formed by processing an oxide film that becomes the oxide 230c.

The oxide 430c functioning as an active layer of the transistor 400 has reduced oxygen vacancies and reduced impurities such as hydrogen and water, similar to the oxide 230 and the like. Accordingly, the threshold voltage of the transistor 400 can be made higher than 0 V, the off-state current can be reduced, and the drain current when the second gate voltage and the first gate voltage are 0 V can be significantly reduced.

<<Dicing line>>
In the following, dicing lines (sometimes called scribe lines, dividing lines, or cutting lines) provided when taking out a plurality of semiconductor devices in the form of chips by dividing a large-area substrate into individual semiconductor elements will be described. . As a dividing method, for example, grooves (dicing lines) for dividing the semiconductor elements are first formed in the substrate, and then cut along the dicing lines to divide (divide) into a plurality of semiconductor devices.

Here, for example, as shown in FIG. 16, it is preferable to design a region where the insulator 254 and the insulator 222 are in contact with each other to form a dicing line. That is, openings are provided in the insulator 224 in the vicinity of a memory cell having a plurality of transistors 200 and a region serving as a dicing line provided on the outer edge of the transistor 400 . Further, an insulator 254 and an insulator 244 are provided so as to cover side surfaces of the insulator 224 .

That is, the insulator 222 and the insulator 254 are in contact with each other at the opening provided in the insulator 224 . For example, at this time, the insulator 222 and the insulator 254 may be formed using the same material and the same method. By providing the insulator 222 and the insulator 254 using the same material and the same method, adhesion can be improved. For example, it is preferable to use aluminum oxide.

With this structure, insulator 222 and insulator 254 can wrap insulator 224 , transistor 200 , and transistor 400 . Since the insulators 222 and 254 have a function of suppressing diffusion of oxygen, hydrogen, and water, the substrate is divided into circuit regions in which the semiconductor elements described in this embodiment are formed. Thus, even if a plurality of chips are processed, impurities such as hydrogen or water can be prevented from entering from the side surfaces of the divided substrates and diffusing into the transistors 200 and 400 .

In addition, this structure can prevent excess oxygen in the insulator 224 from diffusing to the outside of the insulators 254 and 222 . Thus, excess oxygen in insulator 224 is efficiently supplied to the oxide in which the channel in transistor 200 or transistor 400 is formed. The oxygen can reduce oxygen vacancies in the oxide in which a channel is formed in the transistor 200 or the transistor 400 . Accordingly, the oxide semiconductor in which the channel of the transistor 200 or the transistor 400 is formed can have low defect state density and stable characteristics. In other words, variation in electrical characteristics of the transistor 200 or the transistor 400 can be suppressed and reliability can be improved.

This embodiment can be implemented in appropriate combination with the structures described in other embodiments and the like.

(Embodiment 3)
In this embodiment, a transistor using an oxide as a semiconductor (hereinafter also referred to as an OS transistor) and a capacitor according to one embodiment of the present invention are applied with reference to FIGS. A storage device (hereinafter sometimes referred to as an OS memory device) will be described. An OS memory device is a memory device that includes at least a capacitor and an OS transistor that controls charging and discharging of the capacitor. Since the off current of the OS transistor is extremely small, the OS memory device has excellent retention characteristics and can function as a nonvolatile memory.

<Configuration example of storage device>
FIG. 17A shows an example of the configuration of the OS memory device. A memory device 1400 has a peripheral circuit 1411 and a memory cell array 1470 . Peripheral circuitry 1411 includes row circuitry 1420 , column circuitry 1430 , output circuitry 1440 and control logic circuitry 1460 .

Column circuit 1430 has, for example, a column decoder, a precharge circuit, a sense amplifier, a write circuit, and the like. The precharge circuit has a function of precharging the wiring. A sense amplifier has a function of amplifying a data signal read from a memory cell. Note that the above wirings are wirings connected to memory cells included in the memory cell array 1470, and will be described later in detail. The amplified data signal is output to the outside of memory device 1400 via output circuit 1440 as data signal RDATA. Also, the row circuit 1420 has, for example, a row decoder, a word line driver circuit, etc., and can select a row to be accessed.

The storage device 1400 is externally supplied with a low power supply voltage (VSS), a high power supply voltage (VDD) for the peripheral circuit 1411, and a high power supply voltage (VIL) for the memory cell array 1470 as power supply voltages. Control signals (CE, WE, RE), an address signal ADDR, and a data signal WDATA are input to the storage device 1400 from the outside. Address signal ADDR is input to the row and column decoders, and WDATA is input to the write circuit.

The control logic circuit 1460 processes external input signals (CE, WE, RE) to generate control signals for the row decoder and column decoder. CE is a chip enable signal, WE is a write enable signal, and RE is a read enable signal. The signal processed by the control logic circuit 1460 is not limited to this, and other control signals may be input as needed.

Memory cell array 1470 has a plurality of memory cells MC and a plurality of wirings arranged in rows and columns. The number of wirings connecting the memory cell array 1470 and the row circuit 1420 is determined by the configuration of the memory cells MC, the number of memory cells MC in one column, and the like. The number of wires connecting the memory cell array 1470 and the column circuit 1430 is determined by the configuration of the memory cells MC, the number of memory cells MC in one row, and the like.

Note that although FIG. 17A shows an example in which the peripheral circuit 1411 and the memory cell array 1470 are formed on the same plane, this embodiment is not limited to this. For example, as shown in FIG. 17B, a memory cell array 1470 may be provided over part of the peripheral circuit 1411 . For example, a structure in which a sense amplifier is provided under the memory cell array 1470 may be employed.

A configuration example of a memory cell that can be applied to the memory cell MC described above will be described with reference to FIG.

[DOSRAM]
18A to 18C show circuit configuration examples of memory cells of a DRAM. In this specification and the like, a DRAM using a 1-OS-transistor-1-capacitor-type memory cell is sometimes referred to as a DOSRAM (Dynamic Oxide Semiconductor Random Access Memory). A memory cell 1471 illustrated in FIG. 18A includes a transistor M1 and a capacitor CA. Note that the transistor M1 has a gate (sometimes referred to as a front gate) and a back gate.

The transistor M1 has a first terminal connected to the first terminal of the capacitor CA, a second terminal connected to the wiring BIL, a gate connected to the wiring WOL, and a back gate of the transistor M1. are connected to the wiring BGL. A second terminal of the capacitive element CA is connected to the wiring CAL.

The wiring BIL functions as a bit line, and the wiring WOL functions as a word line. The wiring CAL functions as a wiring for applying a predetermined potential to the second terminal of the capacitor CA. A low-level potential is preferably applied to the wiring CAL when data is written and read. The wiring BGL functions as a wiring for applying a potential to the back gate of the transistor M1. By applying an arbitrary potential to the wiring BGL, the threshold voltage of the transistor M1 can be increased or decreased.

Further, the memory cell MC is not limited to the memory cell 1471, and the circuit configuration can be changed. For example, the memory cell MC may have a structure in which the back gate of the transistor M1 is connected to the wiring WOL instead of the wiring BGL, like the memory cell 1472 illustrated in FIG. 18B. Further, for example, the memory cell MC may be a memory cell including a single-gate transistor, that is, a transistor M1 having no back gate, like a memory cell 1473 shown in FIG. 18C.

When the semiconductor device described in any of the above embodiments is used for the memory cell 1471 or the like, the transistor 200 can be used as the transistor M1, and the capacitor 100 can be used as the capacitor CA. By using an OS transistor as the transistor M1, leakage current of the transistor M1 can be significantly reduced. In other words, since written data can be held for a long time by the transistor M1, the frequency of refreshing the memory cell can be reduced. Also, the refresh operation of the memory cells can be made unnecessary. In addition, since leakage current is very low, multilevel data or analog data can be held in the memory cells 1471, 1472, and 1473. FIG.

Further, in the DOSRAM, if the sense amplifier is provided under the memory cell array 1470 as described above, the bit line can be shortened. As a result, the bit line capacity is reduced, and the storage capacity of the memory cell can be reduced.

[NOSRAM]
18D to 18H show a circuit configuration example of a gain cell type memory cell with two transistors and one capacitor. A memory cell 1474 illustrated in FIG. 18D includes a transistor M2, a transistor M3, and a capacitor CB. Note that the transistor M2 has a front gate (sometimes simply referred to as a gate) and a back gate. In this specification and the like, a memory device including a gain cell memory cell using an OS transistor as the transistor M2 is sometimes called a NOSRAM (Nonvolatile Oxide Semiconductor RAM).

The transistor M2 has a first terminal connected to the first terminal of the capacitor CB, a second terminal connected to the wiring WBL, a gate connected to the wiring WOL, and a back gate of the transistor M2. are connected to the wiring BGL. A second terminal of the capacitive element CB is connected to the wiring CAL. A first terminal of the transistor M3 is connected to the wiring RBL, a second terminal of the transistor M3 is connected to the wiring SL, and a gate of the transistor M3 is connected to the first terminal of the capacitor CB.

The wiring WBL functions as a write bit line, the wiring RBL functions as a read bit line, and the wiring WOL functions as a word line. The wiring CAL functions as a wiring for applying a predetermined potential to the second terminal of the capacitor CB. A low-level potential is preferably applied to the wiring CAL when data is written, during data retention, and when data is read. The wiring BGL functions as a wiring for applying a potential to the back gate of the transistor M2. By applying an arbitrary potential to the wiring BGL, the threshold voltage of the transistor M2 can be increased or decreased.

Further, the memory cell MC is not limited to the memory cell 1474, and the circuit configuration can be changed as appropriate. For example, the memory cell MC may have a structure in which the back gate of the transistor M2 is connected to the wiring WOL instead of the wiring BGL, like the memory cell 1475 illustrated in FIG. Further, for example, the memory cell MC may be a memory cell including a single-gate transistor, that is, a transistor M2 having no back gate, like the memory cell 1476 shown in FIG. 18F. Further, for example, the memory cell MC may have a structure in which the wiring WBL and the wiring RBL are combined into one wiring BIL, like the memory cell 1477 illustrated in FIG.

When the semiconductor device described in any of the above embodiments is used for the memory cell 1474 or the like, the transistor 200 can be used as the transistor M2, the transistor 300 can be used as the transistor M3, and the capacitor 100 can be used as the capacitor CB. By using an OS transistor as the transistor M2, the leakage current of the transistor M2 can be very low. Accordingly, written data can be held for a long time by the transistor M2, so that the frequency of refreshing the memory cell can be reduced. Also, the refresh operation of the memory cells can be made unnecessary. In addition, since the leakage current is very low, the memory cell 1474 can hold multilevel data or analog data. Memory cells 1475 to 1477 are similar.

Note that the transistor M3 may be a transistor including silicon in a channel formation region (hereinafter also referred to as a Si transistor). The conductivity type of the Si transistor may be n-channel type or p-channel type. A Si transistor may have higher field effect mobility than an OS transistor. Therefore, a Si transistor may be used as the transistor M3 that functions as a read transistor. Further, by using a Si transistor for the transistor M3, the transistor M2 can be stacked on the transistor M3, so that the area occupied by the memory cell can be reduced and the integration of the memory device can be increased.

Alternatively, the transistor M3 may be an OS transistor. When OS transistors are used for the transistors M2 and M3, the memory cell array 1470 can be configured using only n-channel transistors.

Further, FIG. 18H shows an example of a gain cell type memory cell with three transistors and one capacitor. A memory cell 1478 illustrated in FIG. 18H includes transistors M4 to M6 and a capacitor CC. Capacitive element CC is provided as appropriate. The memory cell 1478 is electrically connected to wirings BIL, RWL, WWL, BGL, and GNDL. A wiring GNDL is a wiring for applying a low-level potential. Note that the memory cell 1478 may be electrically connected to the wirings RBL and WBL instead of the wiring BIL.

The transistor M4 is an OS transistor having a backgate, and the backgate is electrically connected to the wiring BGL. Note that the back gate and gate of the transistor M4 may be electrically connected to each other. Alternatively, transistor M4 may not have a backgate.

Note that the transistors M5 and M6 may each be an n-channel Si transistor or a p-channel Si transistor. Alternatively, the transistors M4 to M6 may be OS transistors. In this case, the memory cell array 1470 can be configured using only n-channel transistors.

When the semiconductor device described in any of the above embodiments is used for the memory cell 1478, the transistor 200 can be used as the transistor M4, the transistor 300 can be used as the transistors M5 and M6, and the capacitor 100 can be used as the capacitor CC. By using an OS transistor as the transistor M4, the leakage current of the transistor M4 can be made very low.

Note that the structures of the peripheral circuit 1411, the memory cell array 1470, and the like described in this embodiment are not limited to those described above. Arrangements or functions of these circuits and wiring, circuit elements, etc. connected to the circuits may be changed, deleted, or added as necessary.

The structure described in this embodiment can be used in combination with any of the structures described in other embodiments or the like as appropriate.

(Embodiment 4)
In this embodiment mode, an example of a chip 1200 on which the semiconductor device of the present invention is mounted is shown with reference to FIG. A plurality of circuits (systems) are mounted on the chip 1200 . Such a technique of integrating a plurality of circuits (systems) on one chip is sometimes called System on Chip (SoC).

As shown in FIG. 19A, a chip 1200 includes a CPU (Central Processing Unit) 1211, a GPU (Graphics Processing Unit) 1212, one or more analog calculation units 1213, one or more memory controllers 1214, one or more interface 1215, one or more network circuits 1216, and the like.

The chip 1200 is provided with bumps (not shown) and is connected to a first surface of a printed circuit board (PCB) 1201 as shown in FIG. 19B. A plurality of bumps 1202 are provided on the back side of the first surface of the PCB 1201 and connected to the motherboard 1203 .

The mother board 1203 may be provided with storage devices such as a DRAM 1221 and a flash memory 1222 . For example, the DOSRAM shown in the previous embodiment can be used for the DRAM 1221 . Further, for example, the NOSRAM described in the above embodiment can be used for the flash memory 1222 .

The CPU 1211 preferably has multiple CPU cores. Also, the GPU 1212 preferably has multiple GPU cores. Also, the CPU 1211 and GPU 1212 may each have a memory for temporarily storing data. Alternatively, a memory common to the CPU 1211 and the GPU 1212 may be provided in the chip 1200 . The above-mentioned NOSRAM or DOSRAM can be used for the memory. Also, the GPU 1212 is suitable for parallel calculation of a large amount of data, and can be used for image processing and sum-of-products operations. By providing the image processing circuit using the oxide semiconductor of the present invention and the product-sum operation circuit in the GPU 1212, image processing and product-sum operation can be performed with low power consumption.

In addition, since the CPU 1211 and the GPU 1212 are provided on the same chip, the wiring between the CPU 1211 and the GPU 1212 can be shortened. And, after the calculation by the GPU 1212, transfer of the calculation result from the GPU 1212 to the CPU 1211 can be performed at high speed.

The analog computation unit 1213 has one or both of an A/D (analog/digital) conversion circuit and a D/A (digital/analog) conversion circuit. Further, the analog calculation unit 1213 may be provided with the sum-of-products calculation circuit.

Memory controller 1214 has a circuit that functions as a controller for DRAM 1221 and a circuit that functions as an interface for flash memory 1222 .

The interface 1215 has an interface circuit with externally connected devices such as a display device, speaker, microphone, camera, and controller. Controllers include mice, keyboards, game controllers, and the like. USB (Universal Serial Bus), HDMI (registered trademark) (High-Definition Multimedia Interface), etc. can be used as such an interface.

The network circuit 1216 has a network circuit such as a LAN (Local Area Network). It may also have circuitry for network security.

The circuit (system) can be formed in the chip 1200 by the same manufacturing process. Therefore, even if the number of circuits required for the chip 1200 increases, there is no need to increase the number of manufacturing processes, and the chip 1200 can be manufactured at low cost.

A PCB 1201 provided with a chip 1200 having a GPU 1212 , a motherboard 1203 provided with a DRAM 1221 and a flash memory 1222 can be referred to as a GPU module 1204 .

Since the GPU module 1204 has the chip 1200 using SoC technology, its size can be reduced. In addition, since it excels in image processing, it is suitable for use in portable electronic devices such as smartphones, tablet terminals, laptop PCs, and portable (portable) game machines. In addition, a product-sum operation circuit using the GPU 1212 enables a deep neural network (DNN), a convolutional neural network (CNN), a recurrent neural network (RNN), an autoencoder, a deep Boltzmann machine (DBM), a deep belief network ( DBN), the chip 1200 can be used as an AI chip, or the GPU module 1204 can be used as an AI system module.

The structure described in this embodiment can be used in appropriate combination with any of the structures described in other embodiments.

(Embodiment 5)
In this embodiment, an application example of a memory device using the semiconductor device described in any of the above embodiments will be described. The semiconductor devices described in the above embodiments are, for example, storage devices of various electronic devices (for example, information terminals, computers, smartphones, electronic book terminals, digital cameras (including video cameras), recording/reproducing devices, navigation systems, etc.). can be applied to Here, the computer includes a tablet computer, a notebook computer, a desktop computer, and a large computer such as a server system. Alternatively, the semiconductor devices described in the above embodiments are applied to various removable storage devices such as memory cards (for example, SD cards), USB memories, and SSDs (solid state drives). FIG. 20 schematically shows some configuration examples of the removable storage device. For example, the semiconductor devices described in the previous embodiments are processed into packaged memory chips and used for various storage devices and removable memories.

FIG. 20A is a schematic diagram of a USB memory. USB memory 1100 has housing 1101 , cap 1102 , USB connector 1103 and substrate 1104 . A substrate 1104 is housed in a housing 1101 . For example, a memory chip 1105 and a controller chip 1106 are attached to the substrate 1104 . The semiconductor device described in any of the above embodiments can be incorporated in the memory chip 1105 of the substrate 1104 or the like.

FIG. 20B is a schematic diagram of the appearance of the SD card, and FIG. 20C is a schematic diagram of the internal structure of the SD card. SD card 1110 has housing 1111 , connector 1112 and substrate 1113 . A substrate 1113 is housed in a housing 1111 . For example, a memory chip 1114 and a controller chip 1115 are attached to the substrate 1113 . By providing a memory chip 1114 also on the back side of the substrate 1113, the capacity of the SD card 1110 can be increased. Alternatively, a wireless chip having a wireless communication function may be provided on the substrate 1113 . As a result, data can be read from and written to the memory chip 1114 by wireless communication between the host device and the SD card 1110 . The semiconductor device described in any of the above embodiments can be incorporated in the memory chip 1114 of the substrate 1113 or the like.

FIG. 20D is a schematic diagram of the appearance of the SSD, and FIG. 20E is a schematic diagram of the internal structure of the SSD. SSD 1150 has housing 1151 , connector 1152 and substrate 1153 . A substrate 1153 is housed in a housing 1151 . For example, substrate 1153 has memory chip 1154 , memory chip 1155 and controller chip 1156 attached thereto. A memory chip 1155 is a work memory for the controller chip 1156, and may be a DOSRAM chip, for example. By providing a memory chip 1154 also on the back side of the substrate 1153, the capacity of the SSD 1150 can be increased. The semiconductor device described in any of the above embodiments can be incorporated in the memory chip 1154 of the substrate 1153 or the like.

This embodiment can be implemented in appropriate combination with the structures described in other embodiments and the like.

(Embodiment 6)
A semiconductor device according to one embodiment of the present invention can be used for a processor such as a CPU or a GPU, or a chip. FIG. 21 illustrates a specific example of an electronic device including a processor such as a CPU or GPU or a chip according to one embodiment of the present invention.

<Electronic Devices/Systems>
A GPU or chip according to one aspect of the present invention can be mounted on various electronic devices. Examples of electronic devices include, for example, televisions, desktop or notebook personal chips, monitors for chips, digital signage (digital signage), and relatively large game machines such as pachinko machines. In addition to electronic devices having a screen, there are digital cameras, digital video cameras, digital photo frames, mobile phones, portable game machines, personal digital assistants, sound reproducing devices, and the like. Further, by providing an electronic device with the integrated circuit or chip according to one embodiment of the present invention, the electronic device can be equipped with artificial intelligence.

An electronic device of one embodiment of the present invention may have an antenna. An image, information, or the like can be displayed on the display portion by receiving a signal with the antenna. Moreover, when an electronic device has an antenna and a secondary battery, the antenna may be used for contactless power transmission.

The electronic device of one embodiment of the present invention includes sensors (force, displacement, position, speed, acceleration, angular velocity, number of rotations, distance, light, liquid, magnetism, temperature, chemical substances, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor or infrared).

An electronic device of one embodiment of the present invention can have various functions. For example, functions to display various information (still images, moving images, text images, etc.) on the display, touch panel functions, functions to display calendars, dates or times, functions to execute various software (programs), wireless communication function, a function of reading a program or data recorded on a recording medium, and the like. FIG. 21 shows an example of an electronic device.

[mobile phone]

FIG. 21A illustrates a mobile phone (smartphone), which is a type of information terminal. The information terminal 5500 includes a housing 5510 and a display portion 5511. As an input interface, the display portion 5511 is provided with a touch panel, and the housing 5510 is provided with buttons.

By applying the chip of one embodiment of the present invention, the information terminal 5500 can execute an application using artificial intelligence. Examples of applications using artificial intelligence include an application that recognizes a conversation and displays the content of the conversation on the display unit 5511, an application that recognizes characters, graphics, etc. input by the user to the touch panel provided in the display unit 5511, An application displayed on the display portion 5511, an application for performing biometric authentication such as a fingerprint or a voiceprint, and the like are given.

[Information terminal 1]
FIG. 21B illustrates a desktop information terminal 5300 . The desktop information terminal 5300 has an information terminal main body 5301 , a display 5302 and a keyboard 5303 .

As with the information terminal 5500 described above, the desktop information terminal 5300 can execute an application using artificial intelligence by applying the chip of one embodiment of the present invention. Examples of applications using artificial intelligence include design support software, text correction software, and automatic menu generation software. Further, by using the desktop information terminal 5300, it is possible to develop new artificial intelligence.

In the above description, a smartphone and a desktop information terminal are shown as examples of electronic devices in FIGS. 21A and 21B, respectively. can. Examples of information terminals other than smart phones and desktop information terminals include PDAs (Personal Digital Assistants), laptop information terminals, and workstations.

[electric appliances]
FIG. 21C shows an electric refrigerator-freezer 5800, which is an example of an electrical appliance. The electric freezer-refrigerator 5800 has a housing 5801, a refrigerator compartment door 5802, a freezer compartment door 5803, and the like.

By applying the chip of one embodiment of the present invention to the electric refrigerator-freezer 5800, the electric refrigerator-freezer 5800 having artificial intelligence can be realized. By using artificial intelligence, the electric freezer-refrigerator 5800 has a function of automatically generating a menu based on the ingredients stored in the electric freezer-refrigerator 5800 and the expiration date of the ingredients, etc. It can have a function of automatically adjusting the temperature according to the ingredients.

In this example, an electric refrigerator/freezer was explained as an electric appliance, but other electric appliances include, for example, a vacuum cleaner, a microwave oven, a microwave oven, a rice cooker, a water heater, an IH cooker, a water server, and an air conditioner. Appliances, washing machines, dryers, audiovisual equipment, etc.

[game machine]

FIG. 21D shows a portable game machine 5200, which is an example of a game machine. The portable game machine includes a housing 5201, a display portion 5202, buttons 5203, and the like.

By applying the GPU or chip of one embodiment of the present invention to the portable game machine 5200, the portable game machine 5200 with low power consumption can be realized. In addition, the low power consumption can reduce the heat generated from the circuit, so that the influence of the heat on the circuit itself, the peripheral circuits, and the module can be reduced.

Furthermore, by applying the GPU or chip of one embodiment of the present invention to the portable game machine 5200, the portable game machine 5200 having artificial intelligence can be realized.

Originally, the progress of the game, the speech and behavior of creatures appearing in the game, and the expressions that occur in the game are determined by the program of the game. , which enables expressions not limited to game programs. For example, it is possible to express changes in the content of questions asked by the player, the progress of the game, the time, and the speech and behavior of characters appearing in the game.

In addition, when a game requiring a plurality of players is played on the portable game machine 5200, since the game players can be configured in an anthropomorphic manner using artificial intelligence, even one person can can play games.

Although FIG. 21D illustrates a portable game machine as an example of a game machine, the game machine to which the GPU or chip of one embodiment of the present invention is applied is not limited to this. Game machines to which the GPU or chip of one aspect of the present invention is applied include, for example, stationary game machines for home use, arcade game machines installed in entertainment facilities (game centers, amusement parks, etc.), and game machines installed in sports facilities. and a pitching machine for batting practice.

[Moving body]
A GPU or chip of one embodiment of the present invention can be applied to automobiles, which are mobile objects, and to the vicinity of the driver's seat of automobiles.

FIG. 21(E1) shows an automobile 5700 which is an example of a moving object, and FIG. 21(E2) is a diagram showing the vicinity of the windshield in the interior of the automobile. FIG. 21E1 illustrates a display panel 5701, a display panel 5702, and a display panel 5703 attached to a dashboard, and a display panel 5704 attached to a pillar.

Display panels 5701 through 5703 can provide a variety of other information such as speedometer, tachometer, mileage, fuel level, gear status, air conditioner settings, and the like. In addition, the display items and layout displayed on the display panel can be appropriately changed according to the user's preference, and the design can be improved. The display panels 5701 to 5703 can also be used as lighting devices.

By displaying an image from an imaging device (not shown) provided in the automobile 5700 on the display panel 5704, the field of view (blind spot) blocked by the pillars can be compensated. That is, by displaying an image from an imaging device provided outside the automobile 5700, blind spots can be compensated for and safety can be enhanced. In addition, by projecting an image that supplements the invisible part, safety confirmation can be performed more naturally and without discomfort. The display panel 5704 can also be used as a lighting device.

Since the GPU or chip of one embodiment of the present invention can be applied as a component of artificial intelligence, the chip can be used in the automatic driving system of the automobile 5700, for example. In addition, the chip can be used in a system for road guidance, danger prediction, and the like. The display panels 5701 to 5704 may be configured to display information such as road guidance and danger prediction.

In addition, in the above description, an automobile is described as an example of a mobile object, but the mobile object is not limited to an automobile. For example, moving objects include trains, monorails, ships, flying objects (helicopters, unmanned aerial vehicles (drones), airplanes, rockets), and the like, and the chip of one embodiment of the present invention can be applied to these moving objects. It is possible to give a system using artificial intelligence.

[Broadcast system]
A GPU or chip of one aspect of the present invention can be applied to a broadcasting system.

FIG. 21(F) schematically shows data transmission in the broadcasting system. Specifically, FIG. 21(F) shows the route of a radio wave (broadcast signal) transmitted from a broadcasting station 5680 reaching a television receiver (TV) 5600 in each home. The TV 5600 includes a receiving device (not shown), and broadcast signals received by the antenna 5650 are transmitted to the TV 5600 via the receiving device.

Although FIG. 21F illustrates a UHF (Ultra High Frequency) antenna as the antenna 5650, a BS/110° CS antenna, a CS antenna, or the like can also be applied as the antenna 5650. FIG.

Radio waves 5675A and 5675B are broadcast signals for terrestrial broadcasting, and radio tower 5670 amplifies received radio waves 5675A and transmits radio waves 5675B. At each home, the antenna 5650 receives the radio wave 5675B, so that the TV 5600 can watch the terrestrial TV broadcast. The broadcasting system is not limited to the terrestrial broadcasting shown in FIG. 21(F), but may be satellite broadcasting using an artificial satellite, data broadcasting using an optical line, or the like.

The above-described broadcasting system may be a broadcasting system using artificial intelligence by applying the chip of one embodiment of the present invention. When broadcast data is transmitted from the broadcasting station 5680 to the TV 5600 in each home, the encoder compresses the broadcast data, and when the antenna 5650 receives the broadcast data, the decoder of the receiving device included in the TV 5600 converts the broadcast data. Restore is done. By using artificial intelligence, for example, it is possible to recognize a display pattern included in a display image in motion compensation prediction, which is one of compression methods of an encoder. Intra-frame prediction using artificial intelligence can also be performed. Further, for example, when receiving low-resolution broadcast data and displaying the broadcast data on a high-resolution TV 5600, image interpolation processing such as up-conversion can be performed in restoring the broadcast data by the decoder.

The above-described broadcasting system using artificial intelligence is suitable for ultra-high definition television (UHDTV: 4K, 8K) broadcasting where the amount of broadcasting data increases.

Also, as an application of artificial intelligence on the TV 5600 side, for example, the TV 5600 may be provided with a recording device having artificial intelligence. With such a configuration, it is possible to automatically record a program that suits the user's taste by having the recording device learn the user's taste using artificial intelligence.

The electronic devices, the functions of the electronic devices, the application examples of artificial intelligence, the effects thereof, and the like described in this embodiment can be appropriately combined with the description of other electronic devices.

This embodiment can be implemented in appropriate combination with the structures described in other embodiments and the like.

100 Capacitor 110 Conductor 112 Conductor 120 Conductor 130 Insulator 150 Insulator 200 Transistor 200A Transistor 203 Conductor 203b Conductor 205 Conductor 205a Conductor 205b Conductor 210 Insulator 212 Insulator 214 Insulator 216 Insulator 218 Conductor 220 Insulator 222 Insulator 224 Insulator 230 Oxide 230a Oxide 230A Oxide film 230b Oxide 230B Oxide film 230c Oxide 230C Oxide film 231 Region 231a Region 231b Region 234 Region 240 Conductor 240a Conductor 240b Conductor 241 Insulator 241a Insulator 241b Insulator 242 Conductor 242a Conductor 242A Conductive film 242B Conductor layer 242b Conductor 243 Region 243a Region 243b Region 244 Insulator 246 Conductor 250 Insulator 250A Insulator 254 Insulator 254A Insulator 255 Insulation Body 255A Insulating film 260 Conductor 260a Conductor 260Aa Conductive film 260Ab Conductive film 260b Conductor 262 Dummy gate 262A Dummy gate layer 273 Insulator 274 Insulator 276 Insulator 280 Insulator 281 Insulator 291 Oxygen 293 Region 300 Transistor 311 Substrate 313 Semiconductor region 314a Low resistance region 314b Low resistance region 315 Insulator 316 Conductor 320 Insulator 322 Insulator 324 Insulator 326 Insulator 328 Conductor 330 Conductor 350 Insulator 352 Insulator 354 Insulator 356 Conductor 400 Transistor 405 Conductive Body 405a Conductor 405b Conductor 430c Oxide 431a Oxide 431b Oxide 432a Oxide 432b Oxide 440 Conductor 440a Conductor 440b Conductor 442 Conductor 442a Conductor 442b Conductor 450 Insulator 460 Conductor 460a Conductor 460b Conductor 1001 Wiring 1002 Wiring 1003 Wiring 1004 Wiring 1005 Wiring 1006 Wiring 1007 Wiring 1008 Wiring 1009 Wiring 1010 Wiring 1100 USB memory 1101 Case 1102 Cap 1103 USB connector 1104 Substrate 1105 Memory chip 1106 Controller chip 1110 SD card 1111 Connector 11132 Case 1111 Substrate 1114 Memory chip 1115 Controller chip 1150 SSD
1151 housing 1152 connector 1153 substrate 1154 memory chip 1155 memory chip 1156 controller chip 1200 chip 1201 PCB
1202 Bump 1203 Motherboard 1204 GPU module 1211 CPU
1212 GPUs
1213 analog operation unit 1214 memory controller 1215 interface 1216 network circuit 1221 DRAM
1222 flash memory 1400 memory device 1411 peripheral circuit 1420 row circuit 1430 column circuit 1440 output circuit 1460 control logic circuit 1470 memory cell array 1471 memory cell 1472 memory cell 1473 memory cell 1474 memory cell 1475 memory cell 1476 memory cell 1477 memory cell 1478 memory cell 5200 Portable game machine 5201 housing 5202 display unit 5203 button 5300 desktop information terminal 5301 main body 5302 display 5303 keyboard 5500 information terminal 5510 housing 5511 display unit 5600 TV
5650 antenna 5670 radio tower 5675A radio wave 5675B radio wave 5680 broadcasting station 5700 automobile 5701 display panel 5702 display panel 5703 display panel 5704 display panel 5800 electric freezer-refrigerator 5801 housing 5802 refrigerator door 5803 freezer door

Claims (10)

a first insulator;
an oxide semiconductor on the first insulator;
a first conductor and a second conductor on the oxide semiconductor;
a second insulator on the oxide semiconductor;
a third conductor located on the second insulator and overlapping with the oxide semiconductor;
the first insulator, the side surface of the oxide semiconductor, the side surface of the first conductor, the top surface of the first conductor, the side surface of the second conductor, the top surface of the second conductor, and a third insulator in contact with a side surface of the second insulator;
the third conductor, the second insulator, and a fourth insulator on the third insulator;
the fourth insulator is in contact with the upper surface of each of the third conductor, the second insulator, and the third insulator;
the first conductor and the second conductor respectively comprise a first element and a second element;
The first element has higher oxidation resistance than the second element,
The semiconductor device, wherein the second element has a smaller work function than the first element. a first insulator;
an oxide semiconductor on the first insulator;
a first conductor and a second conductor on the oxide semiconductor;
a second insulator on the oxide semiconductor;
a third conductor located on the second insulator and overlapping with the oxide semiconductor;
The oxide semiconductor is
a first oxide semiconductor;
a second oxide semiconductor on the first oxide semiconductor;
a third oxide semiconductor on the second oxide semiconductor;
The first insulator, the side surface of the first oxide semiconductor, the side surface of the second oxide semiconductor, the side surface of the first conductor, the top surface of the first conductor, and the second conductor a third insulator in contact with the side surface of the body, the top surface of the second conductor, and the side surface of the third oxide semiconductor;
the third conductor, the second insulator, the third oxide semiconductor, and a fourth insulator on the third insulator;
the fourth insulator is in contact with the top surface of each of the third conductor, the second insulator, the third oxide semiconductor, and the third insulator;
the first conductor and the second conductor respectively comprise a first element and a second element;
The first element has higher oxidation resistance than the second element,
The semiconductor device, wherein the second element has a smaller work function than the first element. In claim 1 or claim 2,
The third insulator and the fourth insulator, respectively,
A semiconductor device that is less permeable to one or both of oxygen and hydrogen than the first insulator. In any one of claims 1 to 3,
The third insulator and the fourth insulator, respectively,
A semiconductor device that is less permeable to one or both of oxygen and hydrogen than the second insulator. In any one of claims 1 to 4,
The third insulator and the fourth insulator, respectively,
A semiconductor device comprising an oxide containing one or both of aluminum and hafnium. In any one of claims 1 to 5,
The semiconductor device, wherein the third insulator and the fourth insulator each contain aluminum oxide. In any one of claims 1 to 6,
The oxide semiconductor is
A semiconductor device containing In, an element M (M is Al, Ga, Y, or Sn), and Zn. In any one of claims 1 to 7,
The oxide semiconductor is
a first region that does not overlap the first conductor and the second conductor;
a second region overlapping the first conductor and the second conductor;
The semiconductor device, wherein the first region has a portion thinner than the second region. In any one of claims 1 to 8,
the first element is one or more of Ru, Rh, Pd, Os, Ir, and Pt;
The second element is Al, Si, Ti, Hf, Zr, Mn, In, Ga, Bi, Ta, Nb, Zn, Sn, Cu, Cr, W, Mo, Ge, Ni, Sc, Y, and A semiconductor device comprising any one or more of Ce. forming a first insulator over the substrate;
forming an oxide film and a first conductive film in this order on the first insulator;
processing the oxide film and the first conductive film to form an oxide semiconductor and a conductor layer;
forming a dummy gate film covering the oxide semiconductor and the conductor layer;
processing the dummy gate film to form a dummy gate layer;
forming a first insulating film covering the first insulator, the oxide semiconductor, the conductor layer, and the dummy gate layer;
forming a second insulating film on the first insulating film;
removing a portion of the first insulating film and the second insulating film until a portion of the dummy gate layer is exposed by performing a first CMP process;
forming a first conductor and a second conductor by etching a portion of the conductor layer and the dummy gate layer to expose the oxide semiconductor;
performing heat treatment to form a third insulating film;
depositing a second conductive film;
By performing a second CMP process, the third insulating film and the second conductive film are removed until part of the second insulating film is exposed, and the third insulator and the third conductive film are removed. forming a conductor,
A method of manufacturing a semiconductor device, comprising forming a fourth insulating film covering the second insulating film, the third insulator, and the third conductor.

Images