TWI623084B - Semiconductor structure and manufacturing method thereof - Google Patents

Abstract

A semiconductor structure includes a substrate, a plurality of first isolation structures disposed in the substrate, at least one buried word line, and at least one second isolation structure. The buried word line intersects the first isolation structure. The second isolation structure intersects the first isolation structure. The material of at least a portion of the second isolation structure is different than the material of the first isolation structure.

Description

Semiconductor structure and method of manufacturing same

The present invention relates to a semiconductor structure and a method of fabricating the same, and more particularly to a semiconductor structure having a buried word line and a method of fabricating the same.

In the fabrication of semiconductor components using buried word lines, intersecting isolation structures are formed in the substrate to define the active regions. However, in the subsequent process of forming the buried word line, both the wet cleaning and the thermal process cause the isolation structure to expand, resulting in a reduction in the size of the active area. Therefore, the contact area between the contact window and the active area also decreases, and the resistance between the contact window and the active area increases. As a result, when the semiconductor element is applied to a memory, the write reply time of the memory is increased, and the operation speed is lowered.

Further, in the process of forming the buried word line, it is easy to form a recess on the isolation structure. Therefore, when the contact window connected to the active region is subsequently formed, the conductor material remains in the recess of the isolation structure, causing a problem of short circuit between the contact windows.

The present invention provides a semiconductor structure and a method of fabricating the same that can effectively prevent size reduction of an active region and avoid a problem of short circuit between contact windows.

The present invention provides a semiconductor structure including a substrate, a plurality of first isolation structures, at least one buried word line, and at least one second isolation structure. The first isolation structure is disposed in the substrate. The buried word line is disposed in the substrate. The buried word line intersects the first isolation structure. The second isolation structure is disposed in the substrate. The second isolation structure intersects the first isolation structure. The material of at least a portion of the second isolation structure is different than the material of the first isolation structure. The bottom surface of at least a portion of the second isolation structure is lower than the top surface of the substrate.

According to an embodiment of the invention, in the semiconductor structure, a gate dielectric layer is further included. The gate dielectric layer is disposed between the buried word line and the substrate. The material of the first isolation structure is, for example, an oxide, and the material of at least a portion of the second isolation structure is, for example, a nitride.

According to an embodiment of the invention, in the above semiconductor structure, the second isolation structure may include a first isolation layer and a second isolation layer. The second isolation layer is between the first isolation layer and the substrate. In a preferred embodiment, the material of the first isolation layer is, for example, a nitride, and the material of the second isolation layer is, for example, an oxide.

According to an embodiment of the invention, in the semiconductor structure, a plurality of active regions are defined by the first isolation structure and the second isolation structure. A top view pattern of the active area on one side of the second isolation structure may extend in a direction in which the positive slope extends, and an upper view pattern of the active area on the other side of the second isolation structure may extend in a direction of a negative slope extend.

According to an embodiment of the invention, in the semiconductor structure, a plurality of active regions are defined by the first isolation structure and the second isolation structure. The top view pattern of the active area on one side and the other side of the second isolation structure may have the same extension direction.

The present invention provides a method of fabricating a semiconductor structure comprising the following steps. A plurality of first isolation structures are formed in the substrate. At least one buried word line is formed in the substrate. The buried word line intersects the first isolation structure. After forming the buried word line, at least one second isolation structure is formed in the substrate. The second isolation structure intersects the first isolation structure.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the method of forming the first isolation structure may include the following steps. A first patterned hard mask layer is formed on the substrate. The first patterned hard mask layer is used as a mask to remove a portion of the substrate, and a plurality of first openings are formed in the substrate. A first isolation structure is formed in the first opening. The method of forming the buried word line may include the following steps. A second patterned hard mask layer is formed on the substrate. The second patterned hard mask layer is used as a mask to remove a portion of the substrate, and at least one second opening is formed in the substrate. A gate dielectric layer is formed on a portion of the surface of the second opening. A buried word line is formed in the second opening.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the method further includes performing an etch back process on the first isolation structure.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the material of at least a portion of the second isolation structure may be different from the material of the first isolation structure.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the method of forming the second isolation structure may include the following steps. A patterned photoresist layer is formed on the substrate. The patterned photoresist layer is used as a mask to remove a portion of the substrate, and at least one third opening is formed in the substrate. The patterned photoresist layer is removed. A first isolation layer filling the third opening is formed.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the method of forming the second isolation structure may further include forming a third opening in the third opening before forming the first isolation layer filling the third opening. Two isolation layers.

According to an embodiment of the present invention, in the method of fabricating the semiconductor structure, the material of the first isolation layer is, for example, a nitride, and the material of the second isolation layer is, for example, an oxide.

Based on the above, in the semiconductor structure proposed by the present invention, since at least a portion of the material of the second isolation structure is different from the material of the first isolation structure, the size of the active region can be effectively prevented from being reduced, and the subsequent formation can be avoided. A problem of short circuit between the contact windows. In this way, the semiconductor structure proposed by the present invention can effectively reduce the write reply time and the elevated operation speed of the semiconductor component, and can improve the product yield, thereby improving the performance and yield of the semiconductor component.

In addition, in the manufacturing method of the semiconductor structure proposed by the present invention, since the second isolation structure is formed after the buried word line is formed first, the thermal process experienced by the second isolation structure can be reduced and the possibility can be reduced. The number of processes for recessing is generated on the second isolation structure, so that the size reduction of the active region can be effectively prevented, and the problem of short circuit between the subsequently formed contact windows can be avoided. In this way, the manufacturing method of the semiconductor structure proposed by the present invention can effectively reduce the write reply time and the elevated operation speed of the semiconductor component, and can improve the product yield, thereby improving the performance and yield of the semiconductor component.

The above described features and advantages of the invention will be apparent from the following description.

1A to 1E are top views of a manufacturing process of a semiconductor structure according to an embodiment of the present invention. 2A to 2E are cross-sectional views taken along line A-A' of Figs. 1A to 1E. 3A to 3E are cross-sectional views taken along line B-B' of Figs. 1A to 1E. 4A to 4E are cross-sectional views taken along line C-C' of Figs. 1A to 1E. The semiconductor structure of the present invention can be implemented in a dynamic random access memory.

Referring to FIGS. 1A, 2A, 3A, and 4A, a first patterned hard mask layer 102 is formed on the substrate 100. Substrate 100 can be a semiconductor substrate, such as a germanium substrate.

The shape of the first patterned hard mask layer 102 is, for example, curved or linear. In this embodiment, the shape of the first patterned hard mask layer 102 is illustrated by taking a curved shape as an example. In the case that the shape of the first patterned hard mask layer 102 is curved, it helps to improve the contact area between the active region and the contact window formed later, so as to reduce the resistance between the contact window and the active region, thereby reducing The write time of the semiconductor component is increased to increase the operating speed.

The first patterned hard mask layer 102 can be a multi-layer structure or a single layer structure. In this embodiment, the first patterned hard mask layer 102 is illustrated by taking a multilayer structure as an example. For example, the first patterned hard mask layer 102 can include a pad oxide layer 104 and a pad nitride layer 106. A pad oxide layer 104 is formed on the substrate 100, and a pad nitride layer 106 is formed on the pad oxide layer 104. The material of the pad oxide layer 104 is, for example, cerium oxide. The material of the pad nitride layer 106 is, for example, tantalum nitride. For example, the pad oxide layer 104 and the pad nitride layer 106 are formed by sequentially forming a pad oxide material layer (not shown) and a pad nitride material layer (not shown), and then the oxide material layer and the pad nitride material. The layer is patterned. The method of forming the pad oxide material layer is, for example, a thermal oxidation method. The method of forming the pad nitride material layer is, for example, a chemical vapor deposition method.

Next, a portion of the substrate 100 is removed with the first patterned hard mask layer 102 as a mask, and a plurality of first openings 108 are formed in the substrate 100. The method of removing part of the substrate 100 is, for example, a dry etching method.

Then, a first isolation structure 110 is formed in the first opening 108. Thereby, a plurality of first isolation structures 110 can be formed in the substrate 100. The material of the first isolation structure 110 is, for example, an oxide such as hafnium oxide. The first isolation structure 110 is formed by, for example, forming a layer of isolation material filling the first opening 108, and then performing an annealing process on the isolation material layer, and removing the isolation material layer other than the first opening 108. The method of forming the layer of the spacer material is, for example, a chemical vapor deposition method. The method of removing the layer of the spacer material other than the first opening 108 is, for example, a chemical mechanical polishing method.

Next, referring to FIG. 1B , FIG. 2B , FIG. 3B and FIG. 4B , the first isolation structure 110 can be selectively etched back to adjust the height of the first isolation structure 110 . The etch back process is, for example, a dry etch process.

Thereafter, the first patterned hard mask layer 102 can be selectively removed. In this embodiment, the pad nitride layer 106 in the first patterned hard mask layer 102 is removed as an example for description. The method of removing the pad nitride layer 106 is, for example, a dry etching method.

A second patterned hard mask layer 112 is then formed over the pad oxide layer 104 over the substrate 100. The second patterned hard mask layer 112 can be a multilayer structure or a single layer structure. In this embodiment, the second patterned hard mask layer 112 is illustrated by taking a multilayer structure as an example. For example, the second patterned hard mask layer 112 can include a hard mask layer 114 and a hard mask layer 116. A hard mask layer 114 is formed on the pad oxide layer 104, and a hard mask layer 116 is formed on the hard mask layer 114. In this embodiment, the material of the hard mask layer 114 is exemplified by ruthenium oxide, and the material of the hard mask layer 116 is exemplified by tantalum carbide. The hard mask layer 114 and the hard mask layer 116 are formed, for example, by a combination of a deposition process and a patterning process, but the invention is not limited thereto. In other embodiments, the second patterned hard mask layer 112 can also be formed by a Self-Align Double Patterning (SADP) process. Moreover, during formation of the second patterned hard mask layer 112, portions of the pad oxide layer 104 on the substrate 100 can be removed simultaneously (as shown in FIG. 4B).

Furthermore, referring to FIG. 1C, FIG. 2C, FIG. 3C and FIG. 4C, the second patterned hard mask layer 112 is used as a mask to remove a portion of the substrate 100, and at least one second opening 118 is formed in the substrate 100. In addition, in the process of removing a portion of the substrate 100, a portion of the first isolation structure 110 is simultaneously removed. The method of removing part of the substrate 100 is, for example, a dry etching method. In addition, in the case where the material of the hard mask layer 116 is made of tantalum carbide, the hard mask layer 116 is simultaneously removed in the process of removing a portion of the substrate 100.

Subsequently, a gate dielectric layer 120 is formed on a portion of the surface of the second opening 118 to isolate the substrate 100 from the subsequently formed buried word line 122. The method of forming the gate dielectric layer 120 is, for example, a thermal oxidation method.

Next, a buried word line 122 is formed in the second opening 118. Thereby, at least one buried word line 122 can be formed in the substrate 100. The buried word line 122 intersects the first isolation structure 110. The top surface of the buried word line 122 is, for example, lower than the top surface of the substrate 100. The material of the buried word line 122 is, for example, a metal or doped polysilicon, wherein the metal can be tungsten (W), TiN (titanium nitride), or a combination thereof. The method for forming the buried word line 122 is, for example, forming a conductor layer (not shown) filling the second opening 118, and then performing an etch back process on the conductor layer. The method of forming the conductor layer is, for example, a physical vapor deposition method or a chemical vapor deposition method. The etch back process is, for example, a dry etch process.

Then, referring to FIG. 1D, FIG. 2D, FIG. 3D and FIG. 4D, a patterned photoresist layer 124 is formed on the hard mask layer 114 above the substrate 100. Additionally, a portion of the patterned photoresist layer 124 can be filled into the second opening 118. The patterned photoresist layer 124 can be formed by a lithography process.

Next, with the patterned photoresist layer 124 as a mask, a portion of the substrate 100 is removed, and at least one third opening 126 is formed in the substrate 100. The method of removing part of the substrate 100 is, for example, a dry etching method.

Referring to FIG. 1E, FIG. 2E, FIG. 3E and FIG. 4E, the film layer above the top surface of the substrate 100 and the first isolation layer 128 in the second opening 118 are omitted in FIG. 1E for clearer operation. Description.

Thereafter, the patterned photoresist layer 124 is removed. The method of removing the patterned photoresist layer 124 is, for example, a dry de-resisting method or a wet de-resisting method.

Next, a first isolation layer 128 filling the third opening 126 is formed, and the first isolation layer 128 located in the third opening 126 can be used as the second isolation structure 130. Thereby, at least one second isolation structure 130 can be formed in the substrate 100 after the buried word line 122 is formed. The second isolation structure 130 intersects the first isolation structure 110. Additionally, a portion of the first isolation layer 128 can be filled into the second opening 118. The material of the first isolation layer 128 is, for example, a nitride such as tantalum nitride. The formation method of the first isolation layer 128 is, for example, a chemical vapor deposition method.

The material of at least a portion of the second isolation structure 130 may be different than the material of the first isolation structure 110. For example, the material of the first isolation structure 110 is, for example, an oxide (eg, hafnium oxide), and the material of at least a portion of the second isolation structure 130 is, for example, a nitride (eg, tantalum nitride). In this embodiment, the material of the second isolation structure 130 is different from the material of the first isolation structure 110 as an example, but the invention is not limited thereto.

The first isolation structure 110 and the second isolation structure 130 define a plurality of active areas AA1. The upper view pattern of the active area AA1 located on one side of the second isolation structure 130 may extend in the extending direction D1 of the positive slope, and the upper view pattern of the active area AA1 located on the other side of the second isolation structure 130 may be negative The slope D2 extends in the extending direction.

In addition, in the case where the material of the second isolation structure 130 is nitrided, the hardness required to isolate the surface of the structure can be achieved without performing a tempering process, thereby preventing the size of the active area AA1 from being reduced, and avoiding the second A recess is formed in the isolation structure 130.

According to the above embodiment, in the manufacturing method of the semiconductor structure, since the second isolation structure 130 is formed after the buried word line 122 is formed first, the thermal process experienced by the second isolation structure 130 can be reduced. And the number of processes that may cause depressions on the second isolation structure 130 is reduced, so that the size reduction of the active area AA1 can be effectively prevented, and the problem of short circuit between the subsequently formed contact windows can be avoided. In this way, the manufacturing method of the semiconductor structure can effectively reduce the writing and returning time of the semiconductor component and improve the operating speed, and can improve the product yield, thereby improving the performance and yield of the semiconductor component. Further, the above-described method of fabricating a semiconductor structure can be applied to processes of various semiconductor elements (e.g., dynamic random access memory).

Hereinafter, the semiconductor structure of this embodiment will be described with reference to FIGS. 1E, 2E, 3E, and 4E.

Referring to FIGS. 1E, 2E, 3E, and 4E, the semiconductor structure includes a substrate 100, a plurality of first isolation structures 110, at least one buried word line 122, and at least one second isolation structure 130. The first isolation structure 110 is disposed in the substrate 100. The buried word line 122 is disposed in the substrate 100. The buried word line 122 intersects the first isolation structure 110. The second isolation structure 130 is disposed in the substrate 100. The second isolation structure 130 intersects the first isolation structure 110. The material of at least a portion of the second isolation structure 130 is different from the material of the first isolation structure 110. The bottom surface of at least a portion of the second isolation structure 130 is lower than the top surface of the substrate 100. In addition, the semiconductor structure may further include a gate dielectric layer 120. The gate dielectric layer 120 is disposed between the buried word line 122 and the substrate 100. In addition, the materials, characteristics, forming methods, and arrangement of the members of the semiconductor structure have been described in detail in the above embodiments, and the description thereof will not be repeated.

Based on the above embodiments, in the above semiconductor structure, since the material of at least a portion of the second isolation structure 130 is different from the material of the first isolation structure 110, the size of the active area AA1 can be effectively prevented from being reduced, and A problem of short circuit between the formed contact windows. In this way, the semiconductor structure can effectively reduce the write return time and the elevated operation speed of the semiconductor component, and can improve the product yield, thereby improving the performance and yield of the semiconductor component.

Figure 5 is a top plan view of a semiconductor structure in accordance with another embodiment of the present invention.

Referring to FIG. 1E and FIG. 5 simultaneously, the structural differences between the semiconductor structure of FIG. 5 and the semiconductor structure of FIG. 1E are explained below. In the semiconductor structure of FIG. 5, a plurality of active regions AA2 are defined by the first isolation structure 110a and the second isolation structure 130. The top view patterns of the plurality of first isolation structures 110a have the same extension direction D3. The upper view pattern of the active area AA2 on one side of the second isolation structure 130 has the same extension direction D4.

In addition, the difference between the manufacturing method of the semiconductor structure of FIG. 5 and the manufacturing method of the semiconductor structure of FIG. 1E is explained below. In the method of fabricating the semiconductor structure of FIG. 1E, the first isolation structure 110 is formed using a curved first patterned hard mask layer 102 (please refer to FIG. 1A). However, in the method of fabricating the semiconductor structure of FIG. 5, a linear patterned hard mask layer (not shown) is used to form the first isolation structure 110a.

Other than that, the semiconductor structure of FIG. 5 is similar to the semiconductor structure of FIG. 1E, and the same components are denoted by the same reference numerals, and thus the description thereof will not be repeated.

Figure 6 is a cross-sectional view taken along line B-B' of Figure 1E in accordance with another embodiment of the present invention. Figure 7 is a cross-sectional view taken along line C-C' of Figure 1E in accordance with another embodiment of the present invention.

Please refer to FIG. 1E, FIG. 3E, FIG. 4E, FIG. 6 and FIG. 7, and the structural differences between the semiconductor structure of FIGS. 6 and 7 and the semiconductor structure of FIGS. 3E and 4E are explained as follows. In the semiconductor structures of FIGS. 6 and 7, the second isolation structure 130a may include a first isolation layer 128 and a second isolation layer 132 in the third opening 126. The second isolation layer 132 is located between the first isolation layer 128 and the substrate 100. The material of the first isolation layer 128 is, for example, a nitride, and the material of the second isolation layer 132 is, for example, an oxide. The material of the top of the second isolation structure 130a (the first isolation layer 128 located in the third opening 126) is different from the material of the first isolation structure 110. The bottom surface of at least a portion of the second isolation structure 130a (eg, the top, ie, the first isolation layer 128 located in the third opening 126) is lower than the top surface of the substrate 100.

Further, in the case where the material of the first isolation layer 128 is nitrided, the top of the second isolation structure 130a (the first isolation layer 128 located in the third opening 126) may have sufficient hardness. Therefore, even if the material of the second isolation layer 132 is made of an oxide, the second isolation layer 132 does not need to be tempered to increase its hardness. In this way, the size of the active area AA1 can be prevented from being reduced, and the occurrence of the recess on the second isolation structure 130a can be avoided. In addition, the dielectric constant of the second isolation layer 132 may be smaller than the dielectric constant of the first isolation layer 128. By selecting the second isolation layer 132 having a lower dielectric constant, the insulation characteristics of the second isolation structure 130a may be improved.

In addition, the differences between the manufacturing method of the semiconductor structure of FIGS. 6 and 7 and the manufacturing method of the semiconductor structure of FIGS. 3E and 4E are explained below. The method of fabricating the semiconductor structure of FIGS. 6 and 7 may further include forming a second isolation layer 132 in the third opening 126 prior to forming the first isolation layer 128 filling the third opening 126. Further, the second isolation layer 132 may be simultaneously formed in the second opening 118. The second isolation layer 132 is formed by, for example, forming a layer of isolation material filling the second opening 118 and the third opening 126, and then removing the isolation material layer outside the second opening 118 and the third opening 126, and more The layer of isolation material located in the second opening 118 and the third opening 126 is subjected to an etch back process. The method of forming the layer of the spacer material is, for example, a chemical vapor deposition method. The method of removing the layer of the spacer material other than the second opening 118 and the third opening 126 is, for example, a chemical mechanical polishing method. The etch back process is, for example, a dry etch process. Except for this, the semiconductor structures of FIGS. 6 and 7 are similar to those of the semiconductor structures of FIGS. 3E and 4E, and the same components are denoted by the same reference numerals, and thus the description thereof will not be repeated.

In summary, the semiconductor structure and the manufacturing method thereof provided by the above embodiments can effectively reduce the write time and the operation speed of the semiconductor device, and can improve the product yield, thereby improving the performance of the semiconductor device. With production.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any one of ordinary skill in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

100‧‧‧Base
102‧‧‧First patterned hard mask layer
104‧‧‧Mat oxide layer
106‧‧‧Material Nitride
108‧‧‧First opening
110, 110a‧‧‧ first isolation structure
112‧‧‧Second patterned hard mask layer
114, 116‧‧‧ hard mask layer
118‧‧‧second opening
120‧‧‧gate dielectric layer
122‧‧‧Blinded word line
124‧‧‧ patterned photoresist layer
126‧‧‧ third opening
128‧‧‧First isolation layer
130, 130a‧‧‧Second isolation structure
132‧‧‧Second isolation
AA1, AA2‧‧‧ active area
D1, D2, D3, D4‧‧‧ extension direction

1A to 1E are top views of a manufacturing process of a semiconductor structure according to an embodiment of the present invention. 2A to 2E are cross-sectional views taken along line A-A' of Figs. 1A to 1E. 3A to 3E are cross-sectional views taken along line B-B' of Figs. 1A to 1E. 4A to 4E are cross-sectional views taken along line C-C' of Figs. 1A to 1E. Figure 5 is a top plan view of a semiconductor structure in accordance with another embodiment of the present invention. Figure 6 is a cross-sectional view taken along line B-B' of Figure 1E in accordance with another embodiment of the present invention. Figure 7 is a cross-sectional view taken along line C-C' of Figure 1E in accordance with another embodiment of the present invention.

Claims (13)

A semiconductor structure comprising: a substrate; a plurality of first isolation structures disposed in the substrate; at least one buried word line disposed in the substrate, wherein the at least one buried word line and the Intersecting the first isolation structures; and at least one second isolation structure disposed in the substrate, wherein the at least one second isolation structure intersects the first isolation structures, and at least a portion of the materials of the at least one second isolation structure Unlike the materials of the first isolation structures, the bottom surface of the at least one portion of the at least one second isolation structure is lower than the top surface of the substrate. The semiconductor structure of claim 1, further comprising a gate dielectric layer disposed between the at least one buried word line and the substrate, wherein the materials of the first isolation structures comprise an oxide And the material of at least a portion of the at least one second isolation structure comprises a nitride. The semiconductor structure of claim 1, wherein the at least one second isolation structure comprises: a first isolation layer; and a second isolation layer between the first isolation layer and the substrate. The semiconductor structure of claim 3, wherein the material of the first isolation layer comprises a nitride, and the material of the second isolation layer comprises an oxide. The semiconductor structure of claim 1, wherein the plurality of active regions are defined by the first isolation structure and the at least one second isolation structure, and the one of the at least one second isolation structure is located on one side of the at least one second isolation structure. The top view pattern of the active region extends in the direction in which the positive slope extends, and the upper view pattern of the active region on the other side of the at least one second isolation structure extends in the direction in which the negative slope extends. The semiconductor structure of claim 1, wherein the first isolation structure and the at least one second isolation structure define a plurality of active regions, and one side of the at least one second isolation structure and another The top view patterns of the active regions on one side have the same extension direction. A method of fabricating a semiconductor structure, comprising: forming a plurality of first isolation structures in a substrate; forming at least one buried word line in the substrate, wherein the at least one buried word line and the first The isolation structures intersect; and after forming the at least one buried word line, at least one second isolation structure is formed in the substrate, wherein the at least one second isolation structure intersects the first isolation structures. The method for fabricating a semiconductor structure according to claim 7, wherein the forming method of the first isolation structures comprises: forming a first patterned hard mask layer on the substrate; The mask layer is a mask, a portion of the substrate is removed, and a plurality of first openings are formed in the substrate; and the first isolation structures are formed in the first openings, and wherein the at least one buried word The method for forming a line includes: forming a second patterned hard mask layer on the substrate; using the second patterned hard mask layer as a mask to remove a portion of the substrate, and forming at least one in the substrate a second opening; forming a gate dielectric layer on a portion of the surface of the at least one second opening; and forming the at least one buried word line in the at least one second opening. The method for fabricating a semiconductor structure according to claim 8, further comprising performing an etch back process on the first isolation structures. The method of fabricating a semiconductor structure according to claim 7, wherein a material of at least a portion of the at least one second isolation structure is different from a material of the first isolation structures. The method for fabricating a semiconductor structure according to claim 7, wherein the forming method of the at least one second isolation structure comprises: forming a patterned photoresist layer on the substrate; using the patterned photoresist layer as a mask a screen, a portion of the substrate is removed, and at least a third opening is formed in the substrate; the patterned photoresist layer is removed; and a first isolation layer filling the at least one third opening is formed. The method of fabricating a semiconductor structure according to claim 11, wherein the forming of the at least one second isolation structure further comprises: before forming the first isolation layer filling the at least one third opening A second isolation layer is formed in at least one of the third openings. The method of fabricating a semiconductor structure according to claim 12, wherein the material of the first isolation layer comprises a nitride, and the material of the second isolation layer comprises an oxide.