JPH11243194A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device on which alignment margin can be increased and the short circuit generation between a contact plug and a gate electrode, etc., can be prevented, and to provide a manufacturing method of the semiconductor device. SOLUTION: An element isolation oxide film 20 is formed on the surface of an n-type silicon substrate 11 through a trench silicon oxide film 17, and an element isolation nitride film 22 is formed on the element isolation oxide film 20. An element region is divided by an element isolation film consisting of the element isolation oxide film 20 and the element isolation nitride film 22. A gate electrode 6 and a gate electrode silicon nitride film 28 are successively formed on the element region. An element isolation side-face silicon nitride film 32 is formed on the sidewall surface of the element isolation film in the region protruding from the surface of the substrate 11. A side-face silicon nitride 31 is formed on the gate electrode 6 and the sidewall surface of the gate electrode silicon nitride film 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can provide a large alignment margin for a contact hole for forming a contact plug electrically connected to a source-drain region or an electrode, and can provide a large space between the contact plug and a substrate. The present invention relates to a semiconductor device capable of preventing occurrence of a short circuit between the semiconductor devices and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic equipment, there has been a demand for integration of semiconductor integrated circuits. The integration of the semiconductor device is achieved by miniaturizing the element size and reducing the alignment margin of various layers constituting the element.
Generally, when designing a mask, a value larger than the alignment accuracy of the lithography technique is considered as an alignment margin. However, the alignment accuracy is
Since it is difficult to improve the size as compared with the degree of miniaturization of the dimensions, techniques for increasing the alignment margin by various manufacturing methods have been conventionally proposed. For example, as a self-aligned contact technique for preventing a short circuit between a contact plug and a wiring layer, a method using a dry etching selectivity between a silicon oxide film and a silicon nitride film has been proposed. In particular, when forming a contact plug for connecting a wiring to a source-drain region of a transistor formed on a surface of a semiconductor substrate, utilizing a dry etching selectivity between a silicon oxide film and a silicon nitride film,
A method of increasing the alignment margin is disclosed (Japanese Patent Laid-Open No. Hei 8-97171).

FIGS. 30 to 41 are sectional views showing a conventional method for manufacturing a semiconductor device in the order of steps. FIG. 42 is a plan view showing the structure of a conventional semiconductor device, and FIG. 43 is a cross-sectional view taken along line DD of FIG. As shown in FIG. 30, first, a buffer oxide film 2 is formed on the surface of a semiconductor substrate 201.
Then, a polycrystalline silicon film 203 is formed on the buffer oxide film 202. Next, a silicon oxide film 204 is formed on the polycrystalline silicon film 203 by a CVD method.

[0004] Next, as shown in FIG. 31, a resist film 260 having a predetermined shape is formed on the silicon oxide film 204, and the silicon oxide film 204, the polycrystalline silicon film 203 and the buffer are formed using the resist film 260 as a mask. The oxide film 202 is selectively etched away. Thereafter, the etching is further continued, and the surface of the substrate 201 is removed by etching from the surface of the semiconductor substrate 201 to a predetermined depth.
06 is provided. Thereafter, the resist film 260 is removed, and then thermal oxidation is performed, so that the inner wall surface of the groove 206 formed in the semiconductor substrate 201 and the polycrystalline silicon film 20 are removed.
A trench silicon oxide film 250 is formed on the side surface of No.3.

After that, as shown in FIG. 32, a groove 206 is buried with a silicon oxide film 207 on the entire surface by the CVD method. Thereafter, as shown in FIG.
7 is selectively removed by etching, and the silicon oxide film 204 is entirely removed by etching, so that the silicon oxide film 207 is left only inside the groove 206. At this time,
The upper surface of the silicon oxide film 207 is
The amount of etching and the like are adjusted so as to be located between the upper surface of the polysilicon film 203 and the upper surface of the polysilicon film 203.

After that, as shown in FIG. 34, a silicon nitride film 208 is deposited on the entire surface by the CVD method. Thereafter, as shown in FIG. 35, the surfaces of the silicon nitride film 208 and the polycrystalline silicon film 203 are selectively polished and flattened by the CMP method, and the silicon nitride film 208 is left only on the silicon oxide film 207. Then, as shown in FIG. 36, after removing all the polycrystalline silicon films 203,
The buffer oxide film 202 is removed by wet etching. The reason why wet etching is used to remove the buffer oxide film 202 is to prevent a damage layer from being formed on the surface of the semiconductor substrate 201 before forming a gate oxide film to be formed later. In this way,
An element isolation film including a silicon oxide film 207 and a silicon nitride film 208 is formed, and an element region is defined by the element isolation film. Thereafter, as shown in FIG. 37, the exposed surface of the semiconductor substrate 201 is thermally oxidized to form the gate oxide film 2.
31 are formed. Thereafter, a polycrystalline silicon film 20 is formed on the entire surface.
9 is deposited, a silicon oxide film 232 is deposited on the polycrystalline silicon film 209.

Then, as shown in FIG. 38, after a resist film 233 having a predetermined shape is formed on the silicon oxide film 232, the silicon oxide film 232 and the polycrystalline silicon are formed using the resist film 233 as a mask. Membrane 209
Is removed by etching to obtain a gate electrode 205 made of a polycrystalline silicon film and a silicon oxide film 211 on the gate electrode on the gate electrode 205.

Then, as shown in FIG. 39, after removing the resist film 233, the silicon oxide film 21 on the gate electrode is removed.
The low concentration n-type diffusion layer 235 is formed on the surface of the substrate 201 by implanting n-type ions into the surface of the semiconductor substrate 201 using the silicon nitride film 208 as a mask.
Thereafter, a silicon oxide film 236 is formed on the entire surface by CVD.
Is deposited. Thereafter, as shown in FIG. 40, the silicon oxide film 236 is etched back. As a result, the silicon oxide film 236 remains on the side wall surfaces of the gate electrode 205 and the silicon oxide film 211 on the gate electrode to obtain the gate side surface silicon oxide film 237 and also on the side wall surface such as the silicon nitride film 208. The silicon oxide film 236 remains, and an element isolation side surface silicon oxide film 238 is obtained. At this time, a part of the gate oxide film 231 on the low concentration n-type diffusion layer 235 is also etched away. Thereafter, an n-type impurity is implanted into the surface of the substrate 201 using the silicon oxide film 211 on the gate electrode, the gate side silicon oxide film 237, the silicon nitride film 208, and the element isolation side silicon oxide film 238 as a mask. Thus, a high-concentration n-type diffusion layer 239 is formed on the surface of the substrate 201, and the LDD (Ligh
A diffusion layer having a tly-doped drain structure is obtained.

Thereafter, as shown in FIG. 41, after an interlayer silicon oxide film 240 is deposited on the entire surface, a resist film 241 of a predetermined shape is formed on the interlayer silicon oxide film 240. Thereafter, using the resist film 241 as a mask, the interlayer silicon oxide film 240 is removed by etching to form a contact hole 242 that reaches the high concentration n-type diffusion layer 239 from the surface of the interlayer silicon oxide film 240. Thereafter, as shown in FIG. 43, after removing the resist film 241, a contact barrier film 243 is deposited. afterwards,
By depositing a conductive film on the entire surface and etching it back, the contact holes 242 are buried with the contact plugs 244 made of the conductive film. After that, a wiring 215 electrically connected to the contact plug 244 is selectively formed.

When a semiconductor device is manufactured in this manner,
Since the etching selectivity between interlayer silicon oxide film 240 and silicon nitride film 208 is different, interlayer silicon oxide film 2
When the contact hole 242 is provided in 40, the silicon nitride film 208 acts as an etching stopper, and the element isolation film composed of the silicon oxide film 207 and the silicon nitride film 208 is not removed by etching. Further, since the silicon nitride film 208 is formed at a position higher than the surface of the semiconductor substrate 201,
And the silicon nitride film 208 do not directly contact.
When the silicon nitride film and the semiconductor substrate are in direct contact,
Since it causes leakage current due to interface order and interface charge, etc., it is possible to prevent contact between both,
Leakage current due to contact between the silicon nitride film and the semiconductor substrate can be prevented.

[0011]

However, the semiconductor device obtained by the above-mentioned conventional manufacturing method has the following problems. That is, when the buffer oxide film 202 is removed by etching, a part of the silicon oxide film 207 protruding from the upper surface of the semiconductor substrate 201 is removed by etching, and a constriction 230 is formed. When the constriction 230 is formed in this manner, a polycrystalline silicon film 209 for a gate electrode is formed after this step, and when the polycrystalline silicon film 209 is selectively removed by etching, The polycrystalline silicon film 209 remains without being removed and becomes a remaining portion 234.

In a subsequent step, if the formation accuracy of the resist film 241 for providing the contact hole 242 in the interlayer silicon oxide film 240 is low, the resist film 24
For example, the contact plug 244 is displaced in the direction indicated by the arrow 210 in FIG. 42. Due to this displacement, when removing the interlayer silicon oxide film 240 to form the contact hole 242, the gate side silicon oxide film 237, the element isolation side silicon oxide film 238, and the like may be removed at the same time. As a result, there is a problem that the remaining portion 234 made of the gate electrode material remaining inside the constriction 230 is electrically connected to the contact plug 244, and a short circuit occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a semiconductor device and a semiconductor device capable of increasing a positioning margin and preventing a short circuit between a contact plug and a substrate or the like. It is intended to provide a manufacturing method.

[0014]

According to the present invention, there is provided a semiconductor device, comprising: a semiconductor substrate; and an element isolation formed on the surface of the semiconductor substrate so that the surface is higher than the surface of the semiconductor substrate. A film, a gate electrode formed on the element region, and a side wall silicon nitride film formed on a side wall surface of the element isolation film protruding from the surface of the semiconductor substrate and on a side wall surface of the gate electrode. It is characterized by the following.

According to another aspect of the present invention, there is provided a semiconductor device having a groove formed on a surface thereof, and a first silicon oxide film buried in the groove such that the surface is higher than the surface of the semiconductor substrate. A first silicon nitride film formed on the first silicon oxide film and forming an element isolation film together with the first silicon oxide film; a gate electrode formed on an element region partitioned by the element isolation film; A second silicon nitride film formed on the gate electrode, a sidewall silicon nitride film formed on a sidewall surface of the element isolation film protruding from the surface of the semiconductor substrate and on a sidewall surface of the gate electrode; A diffusion layer selectively formed on the surface of the element region; an interlayer insulating film formed on the element region and having a contact hole reaching the diffusion layer; and a diffusion layer embedded in the contact hole. And having a contact plug to be gas-connected, the.

This semiconductor device may have a side wall silicon oxide film formed on the side wall silicon nitride film. In this case, the diffusion layer may have an LDD structure. The gate electrode preferably has a polycide structure in which at least one selected from the group consisting of a tungsten silicide film, a titanium silicide film, and a cobalt silicide film is formed on a polysilicon film.

In the method of manufacturing a semiconductor device according to the present invention, a step of forming a groove in a surface of a semiconductor substrate and a step of filling the groove with an element isolation film so that the surface is higher than the surface of the semiconductor substrate Forming a gate electrode on an element region defined by the element isolation film; and forming a sidewall silicon nitride film on a sidewall surface of the element isolation film protruding from a surface of the semiconductor substrate and on a sidewall surface of the gate electrode. And a step of forming

Another method of manufacturing a semiconductor device according to the present invention comprises the steps of forming a first silicon oxide film on a semiconductor substrate, and forming a polycrystalline silicon film on the first silicon oxide film. Forming a groove by selectively removing the polycrystalline silicon film, the first silicon oxide film, and the semiconductor substrate; filling the groove with a second silicon oxide film; and forming an upper surface of the second silicon oxide film. Selectively removing the second silicon oxide film under conditions that are located between the upper surface of the first silicon oxide film and the upper surface of the polycrystalline silicon film, and forming a first silicon nitride film on the entire surface Flattening the surface of the first silicon nitride film to expose the surface of the polycrystalline silicon film, removing the polycrystalline silicon film entirely, and removing the second silicon oxide film and the first silicon nitride film. film Obtaining a Rannahli the isolation layer of the protruded shape from the surface of the semiconductor substrate, the first
Removing the silicon oxide film by wet etching, forming a gate oxide film on the device region partitioned by the device isolation film, and selectively forming a gate electrode on the gate oxide film. Forming a second silicon nitride film on the gate electrode, forming a third silicon nitride film on the entire surface, and etching back the third silicon nitride film to form the gate electrode and the device isolation. Forming a side wall silicon nitride film made of the third silicon nitride film on the side wall surface of the film.

A step of forming an interlayer insulating film over the entire surface after the step of forming the sidewall silicon nitride film, a step of providing a contact hole in the interlayer insulating film, and a step of burying the contact hole with a contact plug; May be provided.

The method may further include a step of forming a sidewall silicon oxide film on the sidewall silicon nitride film. In this case, after the step of forming the sidewall silicon oxide film, an interlayer insulating film is formed on the entire surface. Forming, forming a contact hole in the interlayer insulating film, and burying the contact hole with a contact plug.

Further, a step of forming a third silicon oxide film on the polycrystalline silicon film may be provided between the step of forming the polycrystalline silicon film and the step of forming the trench. In this case, in the step of forming the trench, the third silicon oxide film, the polycrystalline silicon film, the first silicon oxide film, and the semiconductor substrate can be selectively removed.

In the present invention, since the region of the element isolation film protruding from the substrate surface and the gate electrode are covered with the silicon nitride film, a contact plug electrically connected to the diffusion layer on the substrate surface is formed. When the contact hole is formed in the interlayer insulating film, even if the contact hole is displaced and the contact hole protrudes to the element isolation film side, the contact hole penetrates the element isolation film and is formed on the substrate. Never reach.

Further, when the pad silicon oxide film (first silicon oxide film) is removed by wet etching, a part of the interlayer silicon oxide film (second silicon oxide film) constituting the interlayer insulating film is removed and constricted. Is formed,
Even when the gate electrode material remains inside the constriction, since the sidewall silicon nitride film is formed so as to cover the remaining portion of the gate electrode material, the contact plug and the remaining portion of the gate electrode material are formed. But never touch.
Therefore, a short circuit between the contact plug and the substrate can be prevented. Further, in the present invention, even when the contact hole is displaced and protrudes to the gate electrode side, the side wall silicon nitride film is formed on the side wall surface of the gate electrode. Short circuit with the gate electrode can be prevented.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a semiconductor device according to an embodiment of the present invention will be specifically described below with reference to the accompanying drawings. FIG. 1 is a plan view showing a semiconductor device according to a first embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG. As shown in FIGS. 1 and 2, an element isolation oxide film 20 is formed on the surface of an n-type silicon substrate 11 with a trench silicon oxide film 17 interposed therebetween. A nitride film 22 is formed. The element region 2 is defined by the element isolation film 3 having a laminated structure of the element isolation oxide film 20 and the element isolation nitride film 22. On the surface of the element region 2, a high-concentration p-type diffusion layer 35 is selectively formed. On the element region 2 in the region over the high concentration p-type diffusion layer 35,
A gate electrode 6 is formed via a gate oxide film 24, and a silicon nitride film 28 on the gate electrode is formed on the gate electrode 6.

The element isolation nitride film 22 is formed at a position higher than the surface of the n-type silicon substrate 11. Further, a gate oxide film 24 is formed on the side surface of the element isolation oxide film 20 at a position protruding from the surface of the n-type silicon substrate 11.
The constriction is formed by wet etching of the pad silicon oxide film (not shown) before the formation. Inside the constriction, there is a remaining portion 29 made of a gate electrode material after patterning the gate electrode 6 by dry etching. Remaining portion 29 and element isolation nitride film 2 at a position higher than the surface of n-type silicon substrate 11
The element isolation side silicon nitride film 32 is formed on the side wall surface of the gate electrode 2, and the gate side surface silicon nitride film 31 is formed on the side wall surfaces of the gate electrode 6 and the gate electrode silicon nitride film 28. .

Further, the element isolation side silicon nitride film 3
2 and on the side wall surface of the gate side silicon nitride film 31,
An element isolation side surface silicon oxide film 34 and a gate side surface silicon oxide film 33 are formed respectively. On these entire surfaces, an interlayer silicon oxide film 36 having a contact hole reaching the p-type diffusion layer 35 is formed. In this contact hole, a contact plug 40 is formed via a contact barrier film 39, and a wiring 8 electrically connected to the contact plug 40 is formed thereon. The contact hole provided in the interlayer silicon oxide film 36 is displaced in the direction indicated by the arrow 10.

The method of manufacturing the semiconductor device according to the first embodiment thus configured will be described below. FIG.
14 to 14 are cross-sectional views illustrating a method of manufacturing a semiconductor device according to the first embodiment of the present invention in the order of steps. As shown in FIG. 3, a pad silicon oxide film 12 is formed on the n-type silicon substrate 11 to a thickness of about 5 to 20 nm by thermally oxidizing the surface of the n-type silicon substrate 11. Next, CVD
(Chemical vapor deposition) method, the pad silicon oxide film 12
A polycrystalline silicon film 13 having a thickness of 100 to 300 nm is formed thereon. Next, a first silicon oxide film 14 having a thickness of 100 to 300 nm is formed on the polycrystalline silicon film 13 by a CVD method.

Thereafter, as shown in FIG. 4, a resist film 15 is formed on the first silicon oxide film 14, and the resist film 15 is patterned into a shape covering the element region.
Thereafter, using the resist film 15 as a mask, the first silicon oxide film 14, the polycrystalline silicon film 13, and the pad silicon oxide film 12 are selectively removed by dry etching. Thereafter, the etching is further continued to remove the surface of the substrate 11 from the surface of the n-type silicon substrate 11 to a depth of 200 to 500 nm, thereby providing a groove 16.

Thereafter, as shown in FIG.
After removing 5, thermal oxidation is performed to form trench silicon oxide film 17 with a thickness of 5 to 20 nm on the inner wall surface of groove 16 formed in n-type silicon substrate 11. At this time, a polycrystalline silicon sidewall oxide film 18 having a thickness similar to that of trench silicon oxide film 17 is also formed on the end surface of polycrystalline silicon film 13 facing trench 16. afterwards,
A groove 16 is formed on the entire surface by the CVD method at 300 nm to 1 μm.
Embedded in a second silicon oxide film 19 having a thickness of

Then, as shown in FIG. 6, the first silicon formed at a position higher than the upper surface of the polycrystalline silicon film 13 by an etching back method or a combination of a CMP (chemical mechanical polishing) method and an etching method. The oxide film 14 and the second silicon oxide film 19 are selectively removed. Thus, an element isolation oxide film 20 made of the second silicon oxide film remaining inside the trench 16 is obtained. At this time, the upper surface of the element isolation oxide film 20 is located between the upper surface of the pad silicon oxide film 12 and the upper surface of the polycrystalline silicon film 13.
Adjust the amount of etching or polishing.

Thereafter, as shown in FIG. 7, a first silicon nitride film 21 having a thickness of 200 to 300 nm is deposited on the entire surface by the CVD method. Thereafter, as shown in FIG.
The surfaces of the first silicon nitride film 21 and the polycrystalline silicon film 13 are polished by the MP method to planarize the surfaces. Thus, the first silicon nitride film 21 is left only on the element isolation oxide film 20 to obtain the element isolation nitride film 22 made of the first silicon nitride film 21.

Thereafter, as shown in FIG. 9, after removing the entire polycrystalline silicon film 13, the pad silicon oxide film 12 is removed by wet etching. At this time, n
A part of the element isolation oxide film 20 protruding from the surface of the mold silicon substrate 11 is etched away to form a constriction 23. Thereafter, as shown in FIG. 10, the exposed surface of the n-type silicon substrate 11 is thermally oxidized to form a gate oxide film 24 having a thickness of 4 to 15 nm. Thereafter, a polycrystalline silicon film having a thickness of 50 to 200 nm is deposited on the entire surface by the CVD method.
A tungsten silicide film is deposited to a thickness of about 20 nm. Thus, a tungsten polycide film 25 composed of a stacked film of a polycrystalline silicon film and a tungsten silicide film is obtained. Thereafter, a second silicon nitride film 26 having a thickness of 100 to 300 nm is deposited on the tungsten polycide film 25 by the CVD method.

Thereafter, as shown in FIG. 11, after forming a resist film on the entire surface, the resist film is patterned so as to cover a region for forming a gate electrode, thereby obtaining a resist mask 27. Thereafter, by using the resist mask 27 as a mask, the second silicon nitride film 26 and the tungsten polycide film 25 are selectively removed by etching, thereby forming the gate electrode 6 made of the tungsten polycide film 25 and the gate electrode 6 on the gate electrode 6. The silicon nitride film 28 on the gate electrode is obtained. After the second silicon nitride film 26 and the tungsten polycide film 25 are removed by etching, the tungsten polycide film 25 in the constriction 23 is not removed, and the remaining portion 29 remains.

Thereafter, as shown in FIG. 12, after removing the resist mask 27, the silicon nitride film 2 on the gate electrode is removed.
8 and the element isolation nitride film 22 as masks, boron is ion-implanted into the surface of the n-type silicon substrate 11 at a concentration of 2 × 10 ¹³ cm ⁻² , and a heat treatment at 800 to 900 ° C. is performed. A low concentration p-type diffusion layer 30 is formed on the surface. Then, 30 to 1 is applied to the entire surface by CVD.
After depositing a third silicon nitride film (not shown) with a thickness of 00 nm, this third silicon nitride film is etched back. At this time, part of the gate oxide film 24 is also removed, and the low concentration p-type diffusion layer 30 is exposed on the surface. Thereby, the gate electrode 6 and the silicon nitride film 28 on the gate electrode are formed.
The gate side silicon nitride film 31 made of the third silicon nitride film remains on the side wall surface of the semiconductor device, and the element isolation side silicon film made of the third silicon nitride film The nitride film 32 remains.
As a result, the remaining portion 29 is completely confined by the element isolation oxide film 20, the element isolation nitride film 22, and the element isolation side silicon nitride film 32.

Thereafter, as shown in FIG. 13, a third silicon oxide film (not shown) is deposited on the entire surface to a thickness of 50 to 150 nm by CVD, and the third silicon oxide film is etched back. Thereby, the gate side silicon oxide film 33 made of the third silicon oxide film and the third
Element isolation side surface silicon oxide film 3 made of silicon oxide film
4 is formed. Then, the silicon nitride film 2 on the gate electrode
8. Using the silicon oxide film 33 on the gate side surface and the silicon oxide film 34 on the element isolation side as a mask,
Boron is implanted at a concentration of × 10 ¹⁵ cm ^-2 ,
A heat treatment at 00 ° C. is performed. Thus, a high-concentration p-type diffusion layer 35 is formed on the surface of the substrate 11, and a diffusion layer having an LDD structure is obtained.

Thereafter, an interlayer silicon oxide film 36 having a thickness of 300 to 700 nm is deposited on the entire surface, and a resist film 37 is selectively formed on the interlayer silicon oxide film 36. Thereafter, by using the resist film 37 as a mask, the interlayer silicon oxide film 36 is removed by etching to form a contact hole 38 reaching the high concentration p-type diffusion layer 35 from the surface of the interlayer silicon oxide film 36. Thereafter, as shown in FIG. 2, after removing the resist film 37, TiN
And a contact barrier film 39 made of Ti.
Thereafter, a tungsten film is deposited on the entire surface and etched back to fill the contact hole 38 with a contact plug 40 made of a tungsten film.
After that, a wiring 8 made of an aluminum alloy electrically connected to the contact plug 40 is selectively formed. Thus, a p-channel MOSFET is obtained.

In the method of manufacturing a semiconductor device according to the first embodiment, the high-concentration p-type diffusion layer 35 is formed via the contact barrier film 39 made of a titanium film and a titanium nitride film and the contact plug 40 made of tungsten. And is connected to a wiring 8 made of an aluminum alloy. As described above, in order to connect the high-concentration p-type diffusion layer 35 and the wiring 8, the element isolation nitride film 22 and the high-concentration p-type
In addition, it is necessary to form a contact hole 38 reaching the high-concentration p-type diffusion layer 35 in the interlayer silicon oxide film 36 deposited on the silicon nitride film 28 on the gate electrode. At this time, in this embodiment, even if the position of the contact hole 38 is displaced in the direction of the arrow 10 shown in FIG. The nitride film 31 and the device isolation side silicon nitride film 32 function as an etching stopper. Therefore, the contact plug 40 does not reach the remaining portion 29 and a short circuit does not occur between the contact plug 40 and the remaining portion 29. Further, the contact plug 40 does not directly reach the substrate 11 and a short circuit does not occur between the contact plug 40 and the substrate 11.

FIG. 15 is a plan view showing a semiconductor device according to a second embodiment of the present invention. FIG. 16A shows FIG.
FIG. 15 is a sectional view taken along line BB of FIG. 5, and FIG.
It is sectional drawing which follows the CC line of FIG. 15 and 16
Shows an example in which the structure of the semiconductor device according to the present invention is applied to a DRAM memory cell. In the first embodiment, a p-channel MOSFET is described, but the transistor used in the DRAM memory cell in the second embodiment is an n-channel MOSFET.

As shown in FIGS. 15 and 16, an element isolation oxide film 118 is formed on the surface of the p-type silicon substrate 111, and an element isolation nitride film 120 is formed on the element isolation oxide film 118. Have been. The element region 102 is defined by the element isolation oxide film 118 and the element isolation nitride film 120. Also, the p-type silicon substrate 11
A p-channel stopper region 116 is formed in a boundary region between element 1 and element isolation oxide film 118. The source of the n-channel MOSFET is
A low-concentration n-type diffusion layer serving as a drain region is selectively formed. Further, a plurality of band-shaped word lines (gate electrodes) 104 extending in a predetermined direction are formed on the element region 102 in a region extending over the low-concentration n-type diffusion layer 130 via a gate oxide film 122. Word line 1
On the word line 04, a silicon nitride film 126 on the word line is formed. Note that the strip-shaped word lines 104 are also formed on the element isolation nitride films 120 between the element regions 102.

The element isolation nitride film 120 is formed at a position higher than the surface of the p-type silicon substrate 111. Further, the element isolation oxide film 118 formed so as to protrude from the surface of the p-type silicon substrate 111 has a word line 104
The constriction is formed by wet etching of the pad silicon oxide film (not shown) before the formation. The word line 1 is formed by dry etching inside the constriction.
The remaining portion 127 made of the word line material after the patterning of the substrate 04 is present. An element isolation side surface silicon nitride film 129 is formed on the remaining portion 127 and a sidewall surface of the element isolation nitride film 120 at a position higher than the surface of the p-type silicon substrate 111, and the word line 104 and the silicon nitride film on the word line are formed. A word line side silicon nitride film 128 is formed on the side wall surface of 126.

Further, a first interlayer silicon oxide film 134 is formed on the entire surface thereof, and the first interlayer silicon oxide film 134 is provided with a contact hole reaching the low concentration n-type diffusion layer 130. Have been. A bit contact plug 137 is buried in the contact hole, and a bit line 107 extending in a direction perpendicular to the word line 104 is selectively formed on the plug 137 and the first interlayer silicon oxide film 134. ing. Further, a second interlayer silicon oxide film 138 is formed on the entire surface thereof, and a contact hole reaching the low concentration n-type diffusion layer 130 from the surface of the second interlayer silicon oxide film 138 is provided. This contact hole is buried with a capacitor contact plug 140, and this plug 140
The capacitor lower electrode 110 is formed thereon. The bit contact plug 137 and the capacitor contact plug 140 are displaced in the directions indicated by arrows 106 and 109, respectively.

A method for manufacturing the semiconductor device according to the second embodiment having the above-described structure will be described below. FIG.
7 to 29 are sectional views showing a method of manufacturing a semiconductor device according to the second embodiment of the present invention in the order of steps. As shown in FIG. 17, by thermally oxidizing the surface of the p-type silicon substrate 111, about 5 to 20 n
A pad silicon oxide film 112 is formed with a thickness of m. Next, a polycrystalline silicon film 113 having a thickness of 100 to 300 nm is formed on the pad silicon oxide film 112 by a CVD (chemical vapor deposition) method.

Next, as shown in FIG. 18, a resist film 114 having a predetermined shape is formed on the polycrystalline silicon film 113, and using this resist film 114 as a mask, the polycrystalline silicon film 113 and the pad silicon oxide film 112 are formed. Is selectively removed by etching. Thereafter, the etching is further continued, and the surface of the substrate 111 is removed by etching from the surface of the p-type silicon substrate 111 to a predetermined depth to form a groove 115. Thereafter, after the resist film 114 is removed, thermal oxidation is performed under the same conditions as in the first embodiment, whereby n
A trench silicon oxide film 133 is formed on the inner wall surface of the groove 115 formed in the mold silicon substrate 111. Thereafter, the implantation energy is 15 keV and the dose is 2 × 10
After implanting p-type ions into the inner wall surface of the groove 115 at ¹² cm ⁻² , a heat treatment is performed for 10 minutes at a temperature of 900 ° C. in a nitrogen atmosphere to activate the implanted ions and to form a p-channel stopper. A region 116 is formed.

Thereafter, as shown in FIG. 19, a trench 115 is buried in the entire surface with a first silicon oxide film 117 by the CVD method. Thereafter, as shown in FIG. 20, the polysilicon film 113 is selectively removed by an etching back method or a combination of a CMP (Chemical Mechanical Polishing) method and an etching method. As a result, the first remaining in the groove 115
An element isolation oxide film 118 made of a silicon oxide film is obtained.
At this time, the etching amount or the polishing amount is adjusted so that the upper surface of the element isolation oxide film 118 is located between the upper surface of the pad silicon oxide film 112 and the upper surface of the polycrystalline silicon film 113.

Thereafter, as shown in FIG. 21, a first silicon nitride film 119 is deposited on the entire surface by the CVD method. Thereafter, as shown in FIG. 22, the first silicon nitride film 119 is polished by CMP so that the surface becomes flat. As a result, the first silicon nitride film 119 is left only on the element isolation oxide film 118, and the first silicon nitride film 11
9 is obtained.

Thereafter, as shown in FIG. 23, after the polycrystalline silicon film 113 is selectively removed, the pad silicon oxide film 112 is removed by wet etching. As a result, a part of the element isolation oxide film 118 protruding from the upper surface of the p-type silicon substrate 111 is removed by etching.
A constriction 121 is formed. Thereafter, as shown in FIG. 24, the exposed surface of p-type silicon substrate 111 is thermally oxidized to form gate oxide film 122. Thereafter, a polycrystalline silicon film is deposited on the entire surface by the CVD method, and then a tungsten silicide film is deposited on the polycrystalline silicon film. Thus, a tungsten polycide film 123 composed of a stacked film of a polycrystalline silicon film and a tungsten silicide film is obtained. Thereafter, the second silicon nitride film 124 is formed on the tungsten polycide film 123 by the CVD method.
Is deposited.

Thereafter, as shown in FIG. 25, after a resist film 125 having a predetermined shape is formed on the entire surface, the second silicon nitride film 124 and the tungsten polycide film 123 are formed using this resist film 125 as a mask. By selective etching and removal, a word line 104 made of a tungsten polycide film and a silicon nitride film 126 on the word line on the word line 104 are obtained. In addition,
After the second silicon nitride film 124 and the tungsten polycide film 123 are removed by etching, the tungsten polycide film 123 in the constriction 121 is not removed, and the remaining portion 127 is formed.

Thereafter, as shown in FIG. 26, after removing the resist film 125, a third silicon nitride film (not shown) is deposited on the entire surface by CVD, and the third silicon nitride film is etched back. . Thereby, word line 1
04 and the word line side silicon nitride film 128 made of the third silicon nitride film on the side wall surface of the silicon nitride film 126 on the word line and the element isolation nitride film 120.
The element isolation side silicon nitride film 129 made of the third silicon nitride film remains on the side wall surface of the remaining portion 127.
As a result, the remaining portion 127 becomes the element isolation oxide film 118,
The device isolation nitride film 120 and the device isolation side silicon nitride film 129 completely confine the device. Then, after removing the gate oxide film 122 exposed on the surface, the silicon nitride film 126 on the word line and the silicon nitride film 1 on the side of the word line are removed.
28, the p-type silicon substrate 11 using the element isolation nitride film 120 and the element isolation side silicon nitride film 129 as a mask.
By implanting n-type ions into the surface of
A low concentration n-type diffusion layer 130 is formed on the surface of the substrate 1.

Thereafter, as shown in FIG.
After depositing the interlayer silicon oxide film 134, the resist film 13 having a predetermined shape is formed on the first interlayer silicon oxide film 134.
5 is formed. Thereafter, using the resist film 135 as a mask, the first interlayer silicon oxide film 134 is removed by etching, so that the contact hole 13 reaching the low concentration n-type diffusion layer 130 from the surface of the first interlayer silicon oxide film 134 is formed.
6 is provided. Then, as shown in FIG. 28, after removing the resist film 135, an n-type polycrystalline silicon film is deposited on the entire surface and etched back to form a contact hole 136 with a bit made of n-type polycrystalline silicon. It is embedded with a contact plug 137. Thereafter, a tungsten silicide film 131 is formed on the entire surface.

Thereafter, as shown in FIG. 29, the tungsten silicide film 131 is patterned into a predetermined shape to form a bit line 1 made of tungsten silicide electrically connected to the bit contact plug 137.
07 is formed. Thereafter, a second interlayer silicon oxide film 138 is formed on the entire surface, and the second interlayer silicon oxide film 138 is formed.
A resist film 139 having a predetermined shape is formed thereon. Thereafter, the first interlayer silicon oxide film 134 and the second interlayer silicon oxide film 138 are removed by etching using the resist film 139 as a mask to reach the low concentration n-type diffusion layer 130 from the surface of the second interlayer silicon oxide film 138. A contact hole 132 is provided.

Thereafter, as shown in FIG. 16, after the resist film 139 is removed, an n-type polycrystalline silicon film is deposited on the entire surface, and the contact hole 132 is etched back to form the n-type polycrystalline silicon film. Buried with a capacitor contact plug 140 made of Thereafter, an n-type polycrystalline silicon film is formed on the entire surface, and is patterned into a predetermined shape, thereby forming the capacitor lower electrode 110.
Thereafter, a capacitor insulating film (not shown) made of a silicon nitride oxide film having a thickness of 5 nm in terms of a silicon oxide film is formed on the entire surface,
A capacitor upper electrode (not shown) made of n-type polycrystalline silicon is formed at a predetermined position on the capacitor insulating film. Thus, the n-channel M applied to the DRAM memory cell
An OSFET is obtained.

In the semiconductor device according to the second embodiment manufactured as described above, the first interlayer silicon oxide film 1 is also provided.
When the contact holes 136 and 132 are formed in the silicon oxide film 34 and the second interlayer silicon oxide film 138, for example, a displacement of the contact hole 136 occurs in the direction of the arrow 106 shown in FIG. Even when the position shift of 132 occurs and the contact holes 136 and 132 both protrude from the element region 102, the word line side silicon nitride film 128 and the element isolation side silicon nitride film 129 act as an etching stopper. . Therefore, the capacitance contact plug 140 and the bit contact plug 137 reach the remaining portion 127,
It is possible to prevent a short circuit from occurring between these plugs 140 and 137 and the remaining portion 127, and
It is possible to prevent the capacitance contact plug 140 and the bit contact plug 137 from directly reaching the substrate 111 and causing a short circuit between the plugs 140 and 137 and the substrate 111.

In the first and second embodiments, a tungsten polycide film, which is a laminated film of a polycrystalline silicon film and a tungsten silicide film, is used as a material for the gate electrode. The material is not limited to this. For example, a film having a polycide structure in which a titanium silicide film is formed on a polycrystalline silicon film and a film having a polycide structure in which a cobalt silicide film is formed on a polycrystalline silicon film are used. be able to.

[0054]

As described in detail above, according to the present invention,
Since the region of the device isolation film protruding from the substrate surface and the gate electrode are covered with the silicon nitride film, a contact hole can be provided in the interlayer insulating film in a self-aligned manner, and the alignment margin can be increased. Further, even if the contact hole is misaligned and protrudes to the element isolation film side or the gate electrode side, it is necessary to prevent a short circuit between the contact plug and the substrate and a short circuit between the contact plug and the gate electrode. Can be.

[Brief description of the drawings]

FIG. 1 is a plan view showing a semiconductor device according to a first example of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view illustrating a method of manufacturing the semiconductor device according to the first embodiment of the present invention in the order of steps.

FIG. 4 is a sectional view showing a step subsequent to FIG. 3;

FIG. 5 is a sectional view showing a step subsequent to that of FIG. 4;

FIG. 6 is a sectional view showing a step subsequent to FIG. 5;

FIG. 7 is a sectional view showing a step subsequent to FIG. 6;

FIG. 8 is a sectional view showing a step subsequent to FIG. 7;

FIG. 9 is a sectional view showing a step subsequent to FIG. 8;

FIG. 10 is a sectional view showing a step subsequent to that of FIG. 9;

FIG. 11 is a sectional view showing a step subsequent to that of FIG. 10;

FIG. 12 is a sectional view showing a step subsequent to FIG. 11;

FIG. 13 is a sectional view showing a step subsequent to FIG. 12;

FIG. 14 is a sectional view showing a step subsequent to FIG. 13;

FIG. 15 is a plan view showing a semiconductor device according to a second example of the present invention.

16A is a sectional view taken along line BB of FIG. 15, and FIG. 16B is a sectional view taken along line CC of FIG.

FIG. 17 is a sectional view illustrating a method of manufacturing the semiconductor device according to the second embodiment of the present invention in the order of steps.

FIG. 18 is a sectional view showing a step subsequent to FIG. 17;

FIG. 19 is a sectional view showing a step subsequent to that of FIG. 18;

FIG. 20 is a sectional view showing a step subsequent to that of FIG. 19;

FIG. 21 is a sectional view showing a step subsequent to FIG. 20;

FIG. 22 is a sectional view showing a step subsequent to that of FIG. 21.

FIG. 23 is a sectional view showing a step subsequent to FIG. 22;

FIG. 24 is a sectional view showing a step subsequent to FIG. 23;

FIG. 25 is a sectional view showing a step subsequent to FIG. 24;

FIG. 26 is a sectional view showing a step subsequent to that of FIG. 25;

FIG. 27 is a sectional view showing a step subsequent to FIG. 26;

FIG. 28 is a sectional view showing a step subsequent to FIG. 27;

FIG. 29 is a sectional view showing a step subsequent to FIG. 28;

FIG. 30 is a sectional view showing a conventional method of manufacturing a semiconductor device in the order of steps.

FIG. 31 is a sectional view showing a step subsequent to that of FIG. 30;

FIG. 32 is a cross-sectional view showing a step subsequent to that of FIG. 31.

FIG. 33 is a sectional view showing a step subsequent to FIG. 32;

FIG. 34 is a sectional view showing a step subsequent to FIG. 33;

FIG. 35 is a sectional view showing a step subsequent to that of FIG. 34;

FIG. 36 is a cross-sectional view showing a step subsequent to that of FIG. 35.

FIG. 37 is a sectional view showing a step subsequent to FIG. 36;

FIG. 38 is a cross-sectional view showing a step subsequent to that of FIG. 37.

FIG. 39 is a sectional view showing a step subsequent to FIG. 38;

FIG. 40 is a cross-sectional view showing a step subsequent to that of FIG. 39.

FIG. 41 is a cross-sectional view showing a step subsequent to that of FIG. 40.

FIG. 42 is a plan view showing the structure of a conventional semiconductor device.

FIG. 43 is a sectional view taken along line DD of FIG. 42;

[Explanation of symbols]

2, 102; element region 3, element isolation film 6, 205; gate electrode 8, 215; wiring 11, 111; silicon substrate 12, 112; pad silicon oxide film 13, 113, 203, 209; 19, 117, 204, 207, 232, 23
6; silicon oxide film 15, 37, 114, 125, 135, 139, 26
0, 233, 241; resist film 16, 115, 206; groove 17, 133, 250; trench silicon oxide film 18; polycrystalline silicon sidewall oxide film 20, 118; element isolation oxide film 21, 26, 119, 124, 208 Silicon nitride films 22, 120; device isolation nitride films 23, 121, 230; constrictions 24, 122, 231; gate oxide films 25, 123; tungsten polycide film 27; resist mask 28; 127, 234; Remaining portion 30; Low-concentration p-type diffusion layer 31; Gate side silicon nitride films 32, 129; Element isolation side silicon nitride films 34, 238; Element isolation side silicon oxide films 35; High concentration p-type diffusion layer 36 , 134, 138, 240; interlayer silicon oxide films 38, 132, 136, 242; Contact holes 40, 244; contact plugs 104; word lines 107; bit lines 110; capacitance lower electrodes 116; p-channel stopper regions 126; silicon nitride films 128 on word lines; 235; low concentration n-type diffusion layer 131; tungsten silicide film 137; bit contact plug 140; capacitance contact plug 201; semiconductor substrate 202; buffer oxide film 211; silicon oxide film on gate electrode 237;

Claims (10)

[Claims] 1. A semiconductor substrate, an element isolation film formed on the surface of the semiconductor substrate so that the surface is higher than the surface of the semiconductor substrate, and a gate formed on the element region. A semiconductor device comprising: an electrode; and a sidewall silicon nitride film formed on a sidewall surface of an element isolation film protruding from a surface of the semiconductor substrate and on a sidewall surface of the gate electrode. 2. A semiconductor substrate having a groove formed on a surface thereof, a first silicon oxide film buried in the groove such that the surface is higher than the surface of the semiconductor substrate, and a first silicon oxide film formed on the first silicon oxide film. A first silicon nitride film formed thereon to form an element isolation film together with the first silicon oxide film; a gate electrode formed on an element region partitioned by the element isolation film; and a gate electrode formed on the gate electrode A second silicon nitride film, a sidewall silicon nitride film formed on a sidewall surface of a device isolation film protruding from a surface of the semiconductor substrate and a sidewall surface of the gate electrode, and selectively on a surface of the device region. A diffusion layer formed on the element region, an interlayer insulating film having a contact hole formed on the element region and reaching the diffusion layer,
A contact plug buried in the contact hole and electrically connected to the diffusion layer. 3. The semiconductor device according to claim 2, further comprising a side wall silicon oxide film formed on said side wall silicon nitride film, wherein said diffusion layer has an LDD structure. 4. The gate electrode has a polycide structure in which at least one selected from the group consisting of a tungsten silicide film, a titanium silicide film, and a cobalt silicide film is formed on a polysilicon film. Item 4. The semiconductor device according to item 2 or 3. 5. A step of forming a groove in a surface of a semiconductor substrate, a step of burying the groove with an element isolation film so that the surface is higher than the surface of the semiconductor substrate, and being partitioned by the element isolation film. Forming a gate electrode on the formed device region, and forming a sidewall silicon nitride film on a sidewall surface of the device isolation film protruding from the surface of the semiconductor substrate and on a sidewall surface of the gate electrode. A method for manufacturing a semiconductor device, comprising: 6. A step of forming a first silicon oxide film on a semiconductor substrate, a step of forming a polycrystalline silicon film on the first silicon oxide film,
Providing a groove by selectively removing the first silicon oxide film and the semiconductor substrate; burying the groove with a second silicon oxide film; and setting the upper surface of the second silicon oxide film to the first silicon oxide film.
Selectively removing the second silicon oxide film under conditions located between the upper surface of the silicon oxide film and the upper surface of the polycrystalline silicon film; forming a first silicon nitride film on the entire surface; Flattening the surface of the first silicon nitride film to expose the surface of the polycrystalline silicon film, and removing the polycrystalline silicon film entirely to form the second silicon oxide film and the first silicon nitride film. A step of obtaining an element isolation film having a shape protruding from the surface of the semiconductor substrate; a step of removing the first silicon oxide film by wet etching; and forming a gate oxide film on an element region partitioned by the element isolation film. A step of selectively forming a gate electrode on the gate oxide film; a step of forming a second silicon nitride film on the gate electrode; Forming a nitrided film; and forming a sidewall silicon nitride film made of the third silicon nitride film on sidewall surfaces of the gate electrode and the element isolation film by etching back the third silicon nitride film. And a method of manufacturing a semiconductor device. 7. A step of forming an interlayer insulating film over the entire surface after the step of forming the sidewall silicon nitride film, a step of providing a contact hole in the interlayer insulating film, and a step of burying the contact hole with a contact plug. 7. The method for manufacturing a semiconductor device according to claim 6, comprising: 8. The method according to claim 6, further comprising the step of forming a sidewall silicon oxide film on the sidewall silicon nitride film after the step of forming the sidewall silicon nitride film.
13. The method for manufacturing a semiconductor device according to item 5. 9. A step of forming an interlayer insulating film over the entire surface after the step of forming the sidewall silicon oxide film, a step of providing a contact hole in the interlayer insulating film, and a step of burying the contact hole with a contact plug. 9. The method of manufacturing a semiconductor device according to claim 8, comprising: 10. A step of forming a third silicon oxide film on the polycrystalline silicon film between the step of forming the polycrystalline silicon film and the step of forming the groove, Forming the third silicon oxide film in the forming step;
7. The method according to claim 6, wherein the polycrystalline silicon film, the first silicon oxide film, and the semiconductor substrate are selectively removed.
10. The method for manufacturing a semiconductor device according to any one of claims 9 to 9.