semiconductor devices

Abstract

The semiconductor device comprises: a first nitride semiconductor layer; a second nitride semiconductor layer, arranged above the first nitride semiconductor layer, and having a larger band gap than the first nitride semiconductor layer; a first electrode and a second electrode, arranged above the second nitride semiconductor layer; a first insulating film, arranged above the second nitride semiconductor layer, between the first electrode and the second electrode, in contact with the second nitride semiconductor layer, and comprising a first insulating material; a second insulating film, arranged above the second nitride semiconductor layer between the first electrode and the first insulating film, above the first insulating film, and above the second nitride semiconductor layer between the first insulating film and the second electrode, and comprising a second insulating material; a third electrode, arranged above the second insulating film between the first electrode and the first insulating film; and a fourth electrode, having a first electrode portion and a second electrode portion.

Description

[0001] Related applications

[0002] This application claims priority based on Japanese Patent Application No. 2021-38520 (filing date: March 10, 2021), and the entire contents of the basic application are incorporated herein by reference. Technical Field

[0003] The embodiments mainly relate to semiconductor devices. Background Art

[0004] Group III nitrides, such as GaN (gallium nitride) semiconductors, are expected to be the next generation of materials for power semiconductor devices. GaN-based semiconductors have a larger band gap than Si (silicon). Therefore, GaN-based semiconductor devices can achieve smaller and higher-voltage power semiconductor devices compared to Si (silicon) semiconductor devices. Furthermore, this can reduce parasitic capacitance, enabling high-speed power semiconductor devices. Summary of the Invention

[0005] Embodiments of the present invention provide a semiconductor device with improved reliability.

[0006] The semiconductor device of the embodiment comprises: a first nitride semiconductor layer; a second nitride semiconductor layer, arranged above the first nitride semiconductor layer, and having a larger band gap than the first nitride semiconductor layer; a first electrode, arranged above the second nitride semiconductor layer; a second electrode, arranged above the second nitride semiconductor layer; a first insulating film, arranged above the second nitride semiconductor layer, between the first electrode and the second electrode, in contact with the second nitride semiconductor layer, and comprising a first insulating material; a second insulating film, arranged above the second nitride semiconductor layer between the first electrode and the first insulating film, above the first insulating film, and above the second nitride semiconductor layer between the first insulating film and the second electrode, and comprising a second insulating material; a third electrode, arranged above the second insulating film between the first electrode and the first insulating film; and a fourth electrode, comprising: a first electrode portion, arranged above the second insulating film between the third electrode and the first insulating film; and a second electrode portion, arranged above the second insulating film above the first insulating film, and electrically connected to the first electrode portion. In addition, the semiconductor device of the embodiment includes: a first nitride semiconductor layer; a second nitride semiconductor layer, which is arranged above the first nitride semiconductor layer and has a larger band gap than the first nitride semiconductor layer; a first electrode, which is arranged above the second nitride semiconductor layer; a second electrode, which is arranged above the second nitride semiconductor layer; a first insulating film, which is arranged above the second nitride semiconductor layer, between the first electrode and the second electrode, in contact with the second nitride semiconductor layer, and includes a first insulating material; a second insulating film, which is arranged above the second nitride semiconductor layer between the first electrode and the first insulating film, above the first insulating film, and above the second nitride semiconductor layer between the first insulating film and the second electrode, and includes a second insulating material; a third electrode, which is arranged above the second insulating film between the first electrode and the first insulating film; and a fourth electrode, which has: a first electrode portion, which is arranged above the second insulating film between the third electrode and the first insulating film; and a second electrode portion, which is arranged above the second insulating film above the first insulating film and electrically connected to the first electrode portion; and a fifth insulating film, which is arranged between the fourth electrode and the second insulating film. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a schematic cross-sectional view of a semiconductor device according to an embodiment.

[0008] Figure 2 This is a schematic cross-sectional view of a semiconductor device according to another embodiment.

[0009] Figure 3 It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0010] Figure 4It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0011] Figure 5 It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0012] Figure 6 It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0013] Figure 7 It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0014] Figure 8 It is a schematic cross-sectional view of a main part showing a manufacturing process of a semiconductor device according to an embodiment.

[0015] Figure 9 This is a schematic cross-sectional view of a comparative semiconductor device.

[0016] Figure 10 It is a schematic cross-sectional view for explaining the operation and effect of the semiconductor device according to the embodiment. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same reference numerals are given to the same components, and description of components that have been described once will be omitted as appropriate.

[0018] In this specification, the upper direction in the drawings is described as "upper," and the lower direction in the drawings is described as "lower" to indicate the positional relationship of components, etc. In this specification, the concepts of "upper" and "lower" are not necessarily terms that indicate the relationship with the direction of gravity.

[0019] (Implementation Method)

[0020] Figure 1 2 is a schematic cross-sectional view of a semiconductor device 100 according to an embodiment.

[0021] The semiconductor device 100 of the embodiment is a HEMT (High Electron Mobility Transistor) using a nitride semiconductor such as GaN (gallium nitride), AlGaN (aluminum gallium nitride), or InGaN (indium gallium nitride). The semiconductor device 100 of the embodiment has a lateral device structure using a nitride semiconductor.

[0022] The semiconductor device 100 includes a substrate 2, a buffer layer 4, a first nitride semiconductor layer 6, a second nitride semiconductor layer 8, a source electrode (an example of a first electrode) 10, a gate electrode (an example of a third electrode) 12, a drain electrode (an example of a second electrode) 14, a gate field plate electrode 20, a first field plate electrode (an example of a fourth electrode) 30, a second field plate electrode (an example of a fifth electrode) 40, a source field plate electrode (an example of a sixth electrode) 50, a drain field plate electrode 60, a first insulating film 70, a second insulating film 72, a third insulating film 74, a fourth insulating film 76, a fifth insulating film 80, a sixth insulating film 82, a seventh insulating film 84 and an eighth insulating film 86.

[0023] As the substrate 2 , for example, a Si (silicon) substrate or a sapphire substrate is used.

[0024] The buffer layer 4 is provided on the substrate 2. The buffer layer 4 alleviates the lattice mismatch between the buffer layer 4 and the substrate 2. The buffer layer 4 comprises, for example, aluminum gallium nitride (AlGaN). W Ga 1-W N(0<W<1)) multilayer structure.

[0025] The first nitride semiconductor layer 6 is disposed above the buffer layer 4. The first nitride semiconductor layer 6 is, for example, undoped Al X Ga 1-X N (0≤X<1). More specifically, the first nitride semiconductor layer 6 is, for example, undoped GaN. The first nitride semiconductor layer 6 functions as a channel layer. The film thickness of the first nitride semiconductor layer 6 is, for example, not less than 1 μm and not more than 10 μm.

[0026] The second nitride semiconductor layer 8 is disposed above the first nitride semiconductor layer 6. The band gap of the second nitride semiconductor layer 8 is larger than the band gap of the first nitride semiconductor layer 6. The second nitride semiconductor layer 8 is, for example, undoped Al Y Ga 1- Y N (0<Y≤1, X<Y). More specifically, the second nitride semiconductor layer 8 is, for example, undoped Al 0.2 Ga 0.8 N. The second nitride semiconductor layer 8 functions as a barrier layer. The film thickness of the second nitride semiconductor layer 8 is, for example, not less than 15 nm and not more than 50 nm.

[0027] A heterojunction interface is provided between the first nitride semiconductor layer 6 and the second nitride semiconductor layer 8. When the semiconductor device 100 is turned on, a two-dimensional electron gas (2DEG) is formed at the heterojunction interface and serves as carriers.

[0028] In the embodiment, an X-direction, a Y-direction perpendicular to the X-direction, and a Z-direction perpendicular to both the X-direction and the Y-direction are defined. The Z-direction is the direction in which the substrate 2, buffer layer 4, first nitride semiconductor layer 6, and second nitride semiconductor layer 8 are stacked. The substrate 2, buffer layer 4, first nitride semiconductor layer 6, and second nitride semiconductor layer 8 are arranged parallel to the XY plane, which includes an X-axis parallel to the X-direction and a Y-axis parallel to the Y-direction. Furthermore, the interface between the substrate 2 and the buffer layer 4, the interface between the buffer layer 4 and the first nitride semiconductor layer 6, and the interface between the first nitride semiconductor layer 6 and the second nitride semiconductor layer 8 are arranged parallel to the XY plane. The Y-direction is the direction of carrier flow in the semiconductor device 100, which is a HEMT. In other words, the Y-direction is the gate length direction of the semiconductor device 100. The Y-direction is an example of a predetermined direction. The X-direction is the gate width direction of the semiconductor device 100.

[0029] The source electrode 10 is provided on the second nitride semiconductor layer 8. The source electrode 10 functions as a source electrode of the semiconductor device 100. The source electrode 10 includes, for example, a stacked structure of titanium (Ti) and aluminum (Al).

[0030] The drain electrode 14 is provided on the second nitride semiconductor layer 8. The drain electrode 14 serves as a drain electrode of the semiconductor device 100. The drain electrode 14 includes, for example, a stacked structure of titanium (Ti) and aluminum (Al).

[0031] The first insulating film 70 is provided above the second nitride semiconductor layer 8 and between the source electrode 10 and the drain electrode 14. The first insulating film 70 is in direct contact with the second nitride semiconductor layer 8. The first insulating film 70 comprises a first insulating material. Here, the first insulating material is, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), or aluminum oxide (AlO). The film thickness of the first insulating film 70 in the Z direction is, for example, not less than 10 nm and not more than 100 nm.

[0032] The third insulating film 74 is provided above the second nitride semiconductor layer 8 and between the first insulating film 70 and the drain electrode 14. The third insulating film 74 is in direct contact with the second nitride semiconductor layer 8. The third insulating film 74 includes the first insulating material. The thickness of the third insulating film 74 in the Z direction is, for example, not less than 10 nm and not more than 100 nm.

[0033] The fourth insulating film 76 is provided above the second nitride semiconductor layer 8 and between the third insulating film 74 and the drain electrode 14. The fourth insulating film 76 is in direct contact with the second nitride semiconductor layer 8. The fourth insulating film 76 includes the first insulating material. The film thickness of the fourth insulating film 76 in the Z direction is, for example, not less than 10 nm and not more than 100 nm.

[0034] The length L1 of the first insulating film 70 in the direction parallel to the Y direction is preferably less than the length L2 of the third insulating film 74 in the direction parallel to the Y direction. Furthermore, the length L2 of the third insulating film 74 in the direction parallel to the Y direction is preferably less than the length L3 of the fourth insulating film 76 in the direction parallel to the Y direction. In other words, L1 ≤ L2 ≤ L3 is preferably satisfied. For example, the length L1 of the first insulating film 70 in the direction parallel to the Y direction is greater than or equal to 0.5 μm and less than or equal to 1 μm. For example, the length L2 of the third insulating film 74 in the direction parallel to the Y direction is greater than or equal to 0.5 μm and less than or equal to 2 μm. For example, the length L3 of the fourth insulating film 76 in the direction parallel to the Y direction is greater than or equal to 0.5 μm and less than or equal to 3 μm. However, the length L1 of the first insulating film 70 in the direction parallel to the Y direction, the length L2 of the third insulating film 74 in the direction parallel to the Y direction, and the length L3 of the fourth insulating film 76 in the direction parallel to the Y direction are not limited to the above-mentioned lengths.

[0035] The second insulating film 72 is provided above the second nitride semiconductor layer 8 between the source electrode 10 and the first insulating film, on the side surfaces of the first insulating film 70, above the first insulating film 70, above the second nitride semiconductor layer 8 between the first insulating film 70 and the third insulating film 74, on the side surfaces of the third insulating film 74, above the third insulating film 74, above the second nitride semiconductor layer 8 between the third insulating film 74 and the fourth insulating film 76, on the side surfaces of the fourth insulating film 76, above the fourth insulating film 76, and between the fourth insulating film 76 and the drain electrode 14. In other words, the third insulating film 74 is provided between the first insulating film 70 and the drain electrode 14 and between the second nitride semiconductor layer 8 and the second insulating film 72. Furthermore, the fourth insulating film 76 is provided between the third insulating film 74 and the drain electrode 14 and between the second nitride semiconductor layer 8 and the second insulating film 72. The second insulating film 72 includes a second insulating material. Here, the second insulating material is, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), or aluminum oxide (AlO). For example, the second insulating material is silicon nitride (SiN) formed by a plasma CVD (Chemical Vapor Deposition) method, a low-pressure CVD (LPCVD: Low-Pressure Chemical Vapor Deposition) method, or an atomic layer deposition (ALD: Atomic Layer Deposition) method.

[0036] The gate electrode 12 is provided above the second insulating film 72 between the source electrode 10 and the first insulating film 70. The gate electrode 12 may include, for example, a stacked structure of nickel (Ni) and gold (Au), titanium nitride (TiN), or polysilicon (Poly-Si). Preferably, the bottom surface of the gate electrode 12 is in contact with the second insulating film 72.

[0037] The first field plate electrode 30 includes a first electrode portion 32 and a second electrode portion 34. The first electrode portion 32 is provided above the second insulating film 72 between the gate electrode 12 and the first insulating film 70. The bottom surface 32a of the first electrode portion 32 is in contact with the second insulating film 72. The side surface 32b of the first electrode portion 32 is in contact with the second insulating film 72a provided on the side of the first insulating film 70. The second electrode portion 34 is provided above the second insulating film 72 above the first insulating film 70. One end of the second electrode portion 34 is electrically connected to the first electrode portion 32. In other words, when viewed from above, the other end of the second electrode portion 34 is provided between the first electrode portion 32 and the drain electrode 14. The bottom surface 34a of the second electrode portion 34 is in contact with the second insulating film 72b provided above the first insulating film 70. The first field plate electrode 30 is electrically connected to the source electrode 10 using, for example, wiring (not shown) provided in the gate width direction. The first field plate electrode 30 is used to mitigate the electric field within the semiconductor device 100. The first field plate electrode 30 includes, for example, a stacked structure of nickel (Ni) and gold (Au), titanium nitride (TiN), or polysilicon (Poly-Si).

[0038] The length of the first insulating film 70 in the Y direction is shorter than the length of the first field plate electrode 30 in the Y direction.

[0039] The fifth insulating film 80 is provided above the second insulating film 72, above the gate electrode 12, and above the first field plate electrode 30. The fifth insulating film 80 may include, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), or aluminum oxide (AlO). However, the material of the fifth insulating film 80 is not limited thereto.

[0040] The gate field plate electrode 20 includes a first gate field plate electrode portion 22 and a second gate field plate electrode portion 24. For example, one end of the first gate field plate electrode portion 22 is electrically connected to the upper surface of the gate electrode 12. Furthermore, the first gate field plate electrode portion 22 extends upward. The second gate field plate electrode portion 24 is electrically connected to the other end of the first gate field plate electrode portion 22. Furthermore, the second gate field plate electrode portion 24 extends in the gate length direction. However, the form of the gate field plate electrode 20 is not limited to this. The gate field plate electrode 20 is used for electric field relaxation within the semiconductor device 100. The gate field plate electrode 20 includes, for example, Al (aluminum), Cu (copper), W (tungsten), TiN (titanium nitride), or a stacked structure of titanium (Ti) and aluminum (Al).

[0041] The second field plate electrode 40 includes a third electrode portion 42 and a fourth electrode portion 44. The third electrode portion 42 is provided above the second insulating film 72 between the first insulating film 70 and the third insulating film 74. For example, the third electrode portion 42 is provided above the fifth insulating film 80. The fourth electrode portion 44 is provided above the second insulating film 72 above the third insulating film 74. For example, the fourth electrode portion 44 is provided above the fifth insulating film 80a, a portion of the fifth insulating film 80 that protrudes upward, above the third insulating film 74. One end of the fourth electrode portion 44 is electrically connected to the third electrode portion 42. When viewed from above, the other end of the fourth electrode portion 44 is provided between the third electrode portion 42 and the drain electrode 14. The second field plate electrode 40 is electrically connected to the source electrode 10, for example, using a wiring (not shown) provided in the gate width direction. The second field plate electrode 40 serves to mitigate the electric field within the semiconductor device 100. The second field plate electrode 40 includes, for example, Al (aluminum), Cu (copper), W (tungsten), TiN (titanium nitride), or a stacked structure of titanium (Ti) and aluminum (Al).

[0042] The sixth insulating film 82 is provided above the fifth insulating film 80, above the second gate field plate electrode portion 24, and above the second field plate electrode 40. The sixth insulating film 82 may include, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), or aluminum oxide (AlO). However, the material included in the sixth insulating film 82 is not limited thereto.

[0043] The source field plate electrode 50 includes an electrode portion 51, a fifth electrode portion 52, and a sixth electrode portion 54. The electrode portion 51 is electrically connected to the source electrode 10. One end of the electrode portion 51 is, for example, provided above the source electrode 10 and electrically connected thereto, while one end of the fifth electrode portion 52 is electrically connected to the other end of the electrode portion 51. The fifth electrode portion 52 is provided above the source electrode 10, above the gate electrode 12, above the first insulating film 70, above the third insulating film 74, and above the second insulating film 72 between the third insulating film 74 and the fourth insulating film 76. The sixth electrode portion 54 is provided, for example, above the sixth insulating film 82. For example, the sixth electrode portion 54 is provided above the fifth insulating film 80a, a portion of which protrudes upward, and above the sixth insulating film 82a, a portion of which protrudes upward. Furthermore, the sixth insulating film 82a is provided above the fifth insulating film 80b, which is above the fourth insulating film 76. The source field plate electrode 50 is used to relax the electric field in the semiconductor device 100. The source field plate electrode 50 includes, for example, Al (aluminum), Cu (copper), W (tungsten), TiN (titanium nitride), or a stacked structure of titanium (Ti) and aluminum (Al).

[0044] The drain field plate electrode 60 includes a first drain field plate electrode portion 62 and a second drain field plate electrode portion 64. The first drain field plate electrode portion 62 is electrically connected to the drain electrode 14. One end of the first drain field plate electrode portion 62 is, for example, disposed above the drain electrode 14. One end of the first drain field plate electrode portion 62 is, for example, electrically connected to the upper surface of the drain electrode 14. One end of the second drain field plate electrode portion 64 is, for example, electrically connected to the other end of the first drain field plate electrode portion 62. The second drain field plate electrode portion 64 extends toward the source electrode 10. The second drain field plate electrode portion 64 is, for example, disposed above the sixth insulating film 82. The drain field plate electrode 60 is used to mitigate the electric field within the semiconductor device 100. The drain field plate electrode 60 includes, for example, Al (aluminum), Cu (copper), W (tungsten), TiN (titanium nitride), or a stacked structure of titanium (Ti) and aluminum (Al).

[0045] The seventh insulating film 84 is provided above the sixth insulating film 82, above the sixth electrode portion 54, and above the second drain field plate electrode portion 64. The seventh insulating film 84 may include, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), or aluminum oxide (AlO). However, the material included in the seventh insulating film 84 is not limited thereto.

[0046] The eighth insulating film 86 is provided above the seventh insulating film 84. The eighth insulating film 86 may include, for example, silicon oxide (SiO), silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC), silicon nitride (SiN), aluminum nitride (AlN), aluminum oxide (AlO), BCB (benzocyclobutene), or polyimide. However, the material of the eighth insulating film 86 is not limited thereto.

[0047] The shapes of the insulating films of the first insulating film 70, the second insulating film 72, the third insulating film 74, the fourth insulating film 76, the fifth insulating film 80, the sixth insulating film 82, the seventh insulating film 84 and the eighth insulating film 86 and the materials contained in the first insulating film 70, the second insulating film 72, the third insulating film 74, the fourth insulating film 76, the fifth insulating film 80, the sixth insulating film 82, the seventh insulating film 84 and the eighth insulating film 86 can be clarified by analysis using SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and EDX (Energy dispersive X-ray: spectroscopy).

[0048] The first insulating material and the second insulating material are preferably different materials. Here, "different materials" include, for example, the case where both the first and second insulating materials are silicon nitride, but the ratio of silicon to nitrogen differs between the first and second insulating materials. Furthermore, "different materials" include, for example, the case where both the first and second insulating materials are silicon oxide, but the ratio of silicon to oxygen differs between the first and second insulating materials.

[0049] The dielectric constant of the first insulating film 70, the third insulating film 74, or the fourth insulating film 76 is preferably lower than that of the second insulating film 72. In other words, the dielectric constant of the first insulating material is preferably lower than that of the second insulating material.

[0050] The thickness of the first insulating film 70 , the third insulating film 74 , or the fourth insulating film 76 in the Z direction is preferably not less than 10 nm and not more than 100 nm.

[0051] It is preferable that the length of the first insulating film 70 in the Y direction is shorter than the length of the first field plate electrode 30 in the Y direction.

[0052] It is preferable that the length of the third insulating film 74 in the Y direction is shorter than the length of the second field plate electrode 40 in the Y direction.

[0053] The length of the fourth insulating film 76 in the Y direction is preferably shorter than the length of the source field plate electrode 50 in the Y direction.

[0054] Figure 2 This is a schematic cross-sectional view of a semiconductor device 110 according to another embodiment. In semiconductor device 110, first insulating film 70 and first field plate electrode 30 are not provided. Even with such a semiconductor device, preferred embodiments are possible. Furthermore, in semiconductor device 110, second field plate electrode 40 is an example of a fourth electrode, third electrode portion 42 is an example of a first electrode portion, fourth electrode portion 44 is an example of a second electrode portion, source field plate electrode 50 is an example of a fifth electrode, fifth electrode portion 52 is an example of a third electrode portion, sixth electrode portion 54 is an example of a fourth electrode portion, third insulating film 74 is an example of a first insulating film, and fourth insulating film 76 is an example of a third insulating film.

[0055] Figures 3 to 8 Schematic cross-sectional views of main parts showing the manufacturing process of the semiconductor device 100 according to the embodiment.

[0056] First, a buffer layer 4, a first nitride semiconductor layer 6, and a second nitride semiconductor layer 8 are formed on the substrate 2 by, for example, MOCVD (Metal Organic Chemical Vapor Deposition). Next, an insulating film 78 ( Figure 3 ).

[0057] Next, a portion of the insulating film 78 is removed by, for example, wet etching. The removed portions of the insulating film become the first insulating film 70, the third insulating film 74, and the fourth insulating film 76 ( Figure 4 ) Alternatively, a portion of the insulating film 78 may be removed by dry etching, but wet etching is considered to cause less damage to the surface of the second nitride semiconductor layer 8, and therefore wet etching is preferred.

[0058] Next, the second insulating film 72 ( Figure 5 ).

[0059] Next, the gate electrode 12 is formed on the left side of the first insulating film 70 above the second insulating film 72. In addition, the first field plate electrode 30 is formed on the side surface of the second insulating film 72a formed on the side surface of the first insulating film 70 and on the upper surface of the second insulating film 72b formed on the upper surface of the first insulating film 70. At this time, the first electrode portion 32 is formed on the side surface of the second insulating film 72a. In addition, the second electrode portion 34 ( Figure 6 ).

[0060] Figure 7 This diagram illustrates the formation of the fifth insulating film 80 and the second field plate electrode 40. A protruding portion of the fifth insulating film 80, such as the fifth insulating film 80a, is formed on the fifth insulating film 80 formed above the second insulating film 72 above the third insulating film 74. Furthermore, when forming the fifth insulating film 80, a protruding portion of the fifth insulating film 80, such as the fifth insulating film 80b, is formed on the fifth insulating film 80 formed above the second insulating film 72 above the fourth insulating film 76. Furthermore, the third electrode portion 42 is formed on the side surface of the fifth insulating film 80a, and the fourth electrode portion 44 is formed on the upper surface of the fifth insulating film 80a.

[0061] Figure 8This diagram shows the sixth insulating film 82 and the source field plate electrode 50 formed. The sixth insulating film 82 formed above the fifth insulating film 80b has a so-called convex portion of the sixth insulating film 82, such as the sixth insulating film 82a. Furthermore, the fifth electrode portion 52 is formed on the side surface of the sixth insulating film 82a, and the sixth electrode portion 54 is formed on the upper surface of the sixth insulating film 82a.

[0062] Next, the effects of the semiconductor device according to the embodiment will be described.

[0063] Figure 9 1 is a schematic cross-sectional view of a semiconductor device 800 as a comparative embodiment.

[0064] In semiconductor devices using lateral nitride semiconductors, it is difficult to simultaneously achieve a reduction in both the electric field strength around the gate electrode on the drain electrode side and the gate-drain capacitance (Cgd). In a semiconductor device 800 serving as a comparative embodiment, a first field plate electrode 30 is provided on a second insulating film 72 between the gate electrode 12 and the drain electrode 14. This allows for a reduction in both the electric field strength around the gate electrode on the drain electrode side and the gate-drain capacitance (Cgd). However, as semiconductor devices become smaller and the gate-drain distance shortens, there is a problem in that the electric field strength on the drain electrode side of the first field plate electrode 30, particularly at the end 31 of the first field plate electrode 30, increases, thereby reducing the reliability of the semiconductor device. Furthermore, even if the first field plate electrode 30 is not provided, there is a problem in that the electric field strength on the drain electrode side of the gate electrode 12 increases, thereby reducing the reliability of the semiconductor device.

[0065] Therefore, in the semiconductor device of the embodiment, a first field plate electrode 30 is provided, and the first field plate electrode 30 includes: a first electrode portion 32 provided above the second insulating film 72 between the gate electrode 12 and the first insulating film 70; and a second electrode portion 34 provided above the second insulating film 72 above the first insulating film 70 and electrically connected to the first electrode portion 32. Thus, a semiconductor device having no end portion 31 ( Figure 9 ) of the first field plate electrode 30. Figure 10 1 is a schematic cross-sectional view for explaining the effect of the semiconductor device of the embodiment. In other words, it is possible to concentrate the end portion 31 ( Figure 9 ) is distributed over the end portion 32c on the drain electrode 14 side of the bottom surface of the first electrode portion 32 and the end portion 34c on the drain electrode 14 side of the bottom surface of the second electrode portion 34. Thus, a semiconductor device with improved reliability can be provided.

[0066] Furthermore, in the semiconductor device of the embodiment, a second field plate electrode 40 is provided. This second field plate electrode 40 includes a third electrode portion 42 provided above the second insulating film 72 between the first insulating film 70 and the third insulating film 74; and a fourth electrode portion 44 provided above the second insulating film 72 above the third insulating film 74 and electrically connected to the third electrode portion 42. This further disperses the electric field intensity at an end portion 42c of the bottom surface of the fourth electrode portion 44 on the drain electrode 14 side and an end portion 44c of the bottom surface of the fourth electrode portion 44 on the drain electrode 14 side. Consequently, a semiconductor device with improved reliability can be provided.

[0067] Furthermore, the semiconductor device of the embodiment includes a source field plate electrode 50 having a fifth electrode portion 52 disposed above the second insulating film 72 between the third insulating film 74 and the fourth insulating film 76; and a sixth electrode portion 54 disposed above the second insulating film 72 above the fourth insulating film 76 and electrically connected to the fifth electrode portion 52. This further disperses the electric field intensity at an end portion 52c of the bottom surface of the fifth electrode portion 52 on the drain electrode 14 side and an end portion 54c of the bottom surface of the sixth electrode portion 54 on the drain electrode 14 side. Consequently, a semiconductor device with improved reliability can be provided.

[0068] The length of the first insulating film 70 in the Y direction is preferably shorter than the length of the first field plate electrode 30 in the Y direction. The first field plate electrode 30 includes a second electrode portion 34 formed using the upper surface of the first insulating film 70 and a first electrode portion 32 formed using the side surface of the first insulating film 70. Therefore, the length of the first field plate electrode 30 in the Y direction is longer than the length of the first insulating film 70 in the Y direction by at least the amount of the first electrode portion 32.

[0069] The length of the third insulating film 74 in the Y direction is preferably shorter than the length of the second field plate electrode 40 in the Y direction. The second field plate electrode 40 includes a fourth electrode portion 44 formed using the upper surface of the fifth insulating film 80a and a third electrode portion 42 formed using the side surface of the fifth insulating film 80a. Here, the fifth insulating film 80a is formed above the third insulating film 74. Therefore, the length of the fifth insulating film 80a in the Y direction is considered to be equal to or greater than the length of the third insulating film 74 in the Y direction. Therefore, the length of the fourth electrode portion 44 in the Y direction is considered to be equal to the length of the fifth insulating film 80a in the Y direction. Furthermore, the second field plate electrode 40 also includes the third electrode portion 42. Therefore, the length of the third insulating film 74 in the Y direction is shorter than the length of the second field plate electrode 40 in the Y direction.

[0070] Likewise, the length of the fourth insulating film 76 in the Y direction is preferably shorter than the length of the source field plate electrode 50 in the Y direction.

[0071] The length L1 of the first insulating film 70 in the direction parallel to the Y direction is preferably less than or equal to the length L2 of the third insulating film 74 in the direction parallel to the Y direction. Furthermore, the length L2 of the third insulating film 74 in the direction parallel to the Y direction is preferably less than or equal to the length L3 of the fourth insulating film 76 in the direction parallel to the Y direction. In other words, L1 ≤ L2 ≤ L3 is preferably satisfied. This is to ensure that the end portions 32c, 34c, 42c, 44c, 52c, and 54c are appropriately dispersed when viewed from the drain electrode 14, thereby avoiding concentration of electric field intensity.

[0072] The first insulating material and the second insulating material are preferably different. This is to appropriately control the dielectric constant of the first insulating material and the dielectric constant of the second insulating material to avoid concentration of electric field intensity. From this perspective, it is particularly preferred that the dielectric constant of the first insulating material is lower than the dielectric constant of the second insulating material.

[0073] The bottom surface of the first electrode portion 32, the side surfaces of the first electrode portion 32, and the bottom surface of the second electrode portion 34 are preferably in contact with the second insulating film 72. This is because forming the first field plate electrode 30 in this manner facilitates formation of the first field plate electrode 30.

[0074] According to the semiconductor device of the embodiment, it is possible to provide a semiconductor device with improved reliability.

[0075] While several embodiments of the present invention have been described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments may be implemented in various other ways, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. These embodiments and their variations are intended to be within the scope and spirit of the invention and are encompassed by the invention set forth in the claims and their equivalents.

Claims

1. A semiconductor device comprising: a first nitride semiconductor layer; a second nitride semiconductor layer, disposed above the first nitride semiconductor layer, and having a larger band gap than the first nitride semiconductor layer; a first electrode disposed above the second nitride semiconductor layer; a second electrode disposed above the second nitride semiconductor layer; a first insulating film disposed above the second nitride semiconductor layer, between the first electrode and the second electrode, in contact with the second nitride semiconductor layer, and comprising a first insulating material; a second insulating film provided above the second nitride semiconductor layer between the first electrode and the first insulating film, above the first insulating film, and above the second nitride semiconductor layer between the first insulating film and the second electrode, the film comprising a second insulating material; a third electrode disposed above the second insulating film between the first electrode and the first insulating film; as well as A fourth electrode having: a first electrode portion provided above the second insulating film between the third electrode and the first insulating film; and The second electrode portion is provided above the second insulating film above the first insulating film and is electrically connected to the first electrode portion.

2. The semiconductor device according to claim 1, wherein A length of the first insulating film in a predetermined direction intersecting a direction in which the first nitride semiconductor layer and the second nitride semiconductor layer are stacked is shorter than a length of the fourth electrode in the predetermined direction.

3. The semiconductor device according to claim 1, wherein The bottom surface of the first electrode portion, the side surfaces of the first electrode portion, and the bottom surface of the second electrode portion are in contact with the second insulating film.

4. The semiconductor device according to claim 1, wherein The first insulating material is different from the second insulating material.

5. The semiconductor device according to claim 4, wherein The dielectric constant of the first insulating material is lower than the dielectric constant of the second insulating material. The semiconductor device according to claim 1 , wherein: Also features: a third insulating film, provided between the first insulating film and the second electrode and between the second nitride semiconductor layer and the second insulating film, in contact with the second nitride semiconductor layer, and comprising the first insulating material; as well as A fifth electrode having: a third electrode portion provided above the second insulating film between the first insulating film and the third insulating film; and The fourth electrode portion is provided above the second insulating film and above the third insulating film, and is electrically connected to the third electrode portion.

7. The semiconductor device according to claim 6, wherein A length of the third insulating film in a predetermined direction intersecting a direction in which the first nitride semiconductor layer and the second nitride semiconductor layer are stacked is shorter than a length of the fifth electrode in the predetermined direction.

8. The semiconductor device according to claim 6, wherein A length of the first insulating film in a predetermined direction is less than or equal to a length of the third insulating film in the predetermined direction, and the predetermined direction is a direction intersecting a direction in which the first nitride semiconductor layer and the second nitride semiconductor layer are stacked.

9. The semiconductor device according to claim 6, wherein The device further includes a fifth insulating film provided between the second insulating film and the fifth electrode.

10. The semiconductor device according to claim 6, wherein Also features: a fourth insulating film, provided between the third insulating film and the second electrode and between the second nitride semiconductor layer and the second insulating film, in contact with the second nitride semiconductor layer, and comprising the first insulating material; as well as A sixth electrode having: a fifth electrode portion provided above the second insulating film between the third insulating film and the fourth insulating film; and The sixth electrode portion is provided above the second insulating film above the fourth insulating film and is electrically connected to the fifth electrode portion.

11. The semiconductor device according to claim 10, wherein A length of the fourth insulating film in a predetermined direction intersecting a direction in which the first nitride semiconductor layer and the second nitride semiconductor layer are stacked is shorter than a length of the sixth electrode in the predetermined direction.

12. The semiconductor device according to claim 10, wherein Also features: a fifth insulating film provided between the second insulating film and the fifth electrode and between the second insulating film and the sixth electrode; and The sixth insulating film is provided between the fifth insulating film and the sixth electrode.

13. A semiconductor device comprising: a first nitride semiconductor layer; a second nitride semiconductor layer, disposed above the first nitride semiconductor layer, and having a larger band gap than the first nitride semiconductor layer; a first electrode disposed above the second nitride semiconductor layer; a second electrode disposed above the second nitride semiconductor layer; a first insulating film disposed above the second nitride semiconductor layer, between the first electrode and the second electrode, in contact with the second nitride semiconductor layer, and comprising a first insulating material; a second insulating film provided above the second nitride semiconductor layer between the first electrode and the first insulating film, above the first insulating film, and above the second nitride semiconductor layer between the first insulating film and the second electrode, the film comprising a second insulating material; a third electrode disposed above the second insulating film between the first electrode and the first insulating film; A fourth electrode having: a first electrode portion provided above the second insulating film between the third electrode and the first insulating film; and a second electrode portion provided above the second insulating film above the first insulating film and electrically connected to the first electrode portion; as well as The fifth insulating film is provided between the fourth electrode and the second insulating film.

14. The semiconductor device according to claim 13, wherein A length of the first insulating film in a predetermined direction intersecting a direction in which the first nitride semiconductor layer and the second nitride semiconductor layer are stacked is shorter than a length of the fourth electrode in the predetermined direction.

15. The semiconductor device according to claim 13, wherein The bottom surface of the first electrode portion, the side surfaces of the first electrode portion, and the bottom surface of the second electrode portion are in contact with the second insulating film.

16. The semiconductor device according to claim 13, wherein The first insulating material is different from the second insulating material.

17. The semiconductor device according to claim 16, wherein The dielectric constant of the first insulating material is lower than the dielectric constant of the second insulating material.

18. The semiconductor device according to claim 13, wherein have: a third insulating film, provided between the first insulating film and the second electrode and between the second nitride semiconductor layer and the second insulating film, in contact with the second nitride semiconductor layer, and comprising the first insulating material; A fifth electrode having: a third electrode portion provided above the second insulating film between the first insulating film and the third insulating film; and a fourth electrode portion provided above the second insulating film above the third insulating film and electrically connected to the third electrode portion; as well as The sixth insulating film is provided between the fifth insulating film and the fifth electrode.

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