Semiconductor device and manufacturing method thereof

Abstract

To provide a semiconductor device with stable characteristics and a manufacturing method thereof.SOLUTION: A semiconductor device according to an embodiment includes first to third electrodes and a semiconductor member. The first semiconductor layer includes Alx1Ga1-x1N (0≤x1<1). The second semiconductor layer includes Alx2Ga1-x2N (0<x2<1, x1<x2). The third semiconductor layer includes Al, Ga, and N. At least a portion of the third semiconductor layer is provided between a third semiconductor portion of the second semiconductor layer and at least a portion of a second electrode portion of the second electrode. The third semiconductor layer includes a first portion including Aly1Ga1-y1N (0<y1≤1) and a second portion including Aly2Ga1-y2N (0≤y2<1, y2<y1). The second portion is between the first portion and at least a portion of the second electrode portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a semiconductor device and a manufacturing method thereof. [Background technology]

[0002] For example, stable characteristics are desired in semiconductor devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-537713 Summary of the Invention [Problem to be solved by the invention]

[0004] The embodiments of the present invention provide a semiconductor device capable of stabilizing characteristics and a method for manufacturing the same. [Means for solving the problem]

[0005] According to an embodiment of the present invention, a semiconductor device includes a first electrode, a second electrode, a third electrode, and a semiconductor member. A direction from the first electrode to the second electrode is along a first direction. The second electrode includes a first electrode portion and a second electrode portion. The second electrode portion is connected to the first electrode portion. The position of the third electrode in the first direction is between the position of the first electrode in the first direction and the position of the second electrode in the first direction. The semiconductor member includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. The first semiconductor layer is Al x1 Ga 1-x1It includes N(0≦x1<1). The first semiconductor layer includes a first partial region, a second partial region, a third partial region, a fourth partial region, a fifth partial region, and a sixth partial region. The second direction from the first partial region to the first electrode intersects the first direction. The direction from the second partial region to the first electrode portion is along the second direction. The direction from the sixth partial region to the second electrode portion is along the second direction. The direction from the third partial region to the third electrode is along the second direction. The position of the fourth partial region in the first direction is between the position of the first partial region in the first direction and the position of the third partial region in the first direction. The position of the fifth partial region in the first direction is between the position of the third partial region in the first direction and the position of the second partial region in the first direction. The position of the sixth partial region in the first direction is between the position of the fifth partial region in the first direction and the position of the second partial region in the first direction. The second semiconductor layer contains Al x2 Ga 1-x2 It contains N(0<x2<1, x1<x2). The second semiconductor layer includes a first semiconductor part, a second semiconductor part, and a third semiconductor part. The direction from the fourth partial region to the first semiconductor part is along the second direction. The direction from the fifth partial region to the second semiconductor part is along the second direction. The direction from the sixth partial region to the third semiconductor part is along the second direction. The third semiconductor layer contains Al, Ga, and N. At least a part of the third semiconductor layer is provided between the third semiconductor part and at least a part of the second electrode part in the second direction. The third semiconductor layer contains Al y1 Ga 1-y1 It includes a first part containing N(0<y1≦1) and Al y2 Ga 1-y2 It includes a second part containing N(0≦y2<1, y2<y1). The second part is between the first part and at least a part of the second electrode part.

Brief Description of the Drawings

[0006] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a semiconductor device according to the first embodiment. [Figure 2] FIG. 2 is a schematic plan view illustrating the semiconductor device according to the first embodiment. [Figure 3] FIG. 3 is a schematic view illustrating the semiconductor device according to the first embodiment. [Figure 4] FIG. 4 is a schematic view illustrating the semiconductor device according to the first embodiment. [Figure 5] FIG. 5 is a schematic view illustrating the semiconductor device according to the first embodiment. [Figure 6] FIG. 6 is a schematic view illustrating the semiconductor device according to the first embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 9] 9(a) to 9(c) are schematic views illustrating the semiconductor device according to the first embodiment. [Figure 10] 10(a) to 10(c) are schematic views illustrating the semiconductor device according to the first embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 13] FIG. 13 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 14] FIG. 14 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. [Figure 15] 15(a) to 15(c) are schematic cross-sectional views illustrating the method for manufacturing the semiconductor device according to the second embodiment. [Figure 16] 16A and 16B are schematic cross-sectional views illustrating the method for manufacturing the semiconductor device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and in each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0008] (First embodiment)

[0009] FIG. 1 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. FIG. 2 is a schematic plan view illustrating the semiconductor device according to the first embodiment. FIG. 1 is a cross-sectional view taken along line A1-A2 in FIG.

[0010] As shown in FIGS. 1 and 2, a semiconductor device 110 according to the embodiment includes a first electrode 51, a second electrode 52, a third electrode 53, and a semiconductor member 10M.

[0011] The direction from the first electrode 51 to the second electrode 52 is along the first direction D1. The first direction D1 is the X-axis direction. One direction perpendicular to the X-axis direction is the Z-axis direction. The direction perpendicular to the X-axis and Z-axis directions is the Y-axis direction.

[0012] 1, the second electrode 52 includes a first electrode portion 52a and a second electrode portion 52b. The second electrode portion 52b is connected to the first electrode portion 52a.

[0013] The position of the third electrode 53 in the first direction D1 is between the position of the first electrode 51 in the first direction D1 and the position of the second electrode 52 in the first direction D1.

[0014] The semiconductor member 10M includes a first semiconductor layer 10, a second semiconductor layer 20, and a third semiconductor layer 30.

[0015] The first semiconductor layer 10 contains Al x1 Ga 1-x1 N (0 ≦ x1 < 1). The composition ratio x1 is, for example, 0 or more and less than 0.15. The first semiconductor layer 10 may be, for example, a GaN layer.

[0016] The first semiconductor layer 10 includes a first partial region 11, a second partial region 12, a third partial region 13, a fourth partial region 14, a fifth partial region 15, and a sixth partial region 16. The second direction D2 from the first partial region 11 to the first electrode 51 intersects the first direction D1. The second direction D2 may be, for example, the Z-axis direction.

[0017] The direction from the second partial region 12 to the first electrode portion 52a is along the second direction D2. The direction from the sixth partial region 16 to the second electrode portion 52b is along the second direction D2. The direction from the third partial region 13 to the third electrode 53 is along the second direction D2.

[0018] The position of the fourth partial region 14 in the first direction D1 is between the position of the first partial region 11 in the first direction D1 and the position of the third partial region 13 in the first direction D1. The position of the fifth partial region 15 in the first direction D1 is between the position of the third partial region 13 in the first direction D1 and the position of the second partial region 12 in the first direction D1. The position of the sixth partial region 16 in the first direction D1 is between the position of the fifth partial region 15 in the first direction D1 and the position of the second partial region 12 in the first direction D1.

[0019] The second semiconductor layer 20 contains Al x2 Ga 1-x2 N (0 < x2 < 1, x1 < x2). The composition ratio x2 may be, for example, 0.15 or more and 0.4 or less. The second semiconductor layer 20 is, for example, an AlGaN layer.

[0020] The second semiconductor layer 20 includes a first semiconductor portion 21, a second semiconductor portion 22, and a third semiconductor portion 23. The direction from the fourth partial region 14 to the first semiconductor portion 21 is along the second direction D2. The direction from the fifth partial region 15 to the second semiconductor portion 22 is along the second direction D2. The direction from the sixth partial region 16 to the third semiconductor portion 23 is along the second direction D2.

[0021] The third semiconductor layer 30 includes, for example, Al, Ga, and N. The third semiconductor layer 30 may be, for example, an AlGaN layer. At least a part of the third semiconductor layer 30 is provided between the third semiconductor portion 23 and at least a part of the second electrode portion 52b in the second direction D2.

[0022] The third semiconductor layer 30 includes, for example, a first portion 31 and a second portion 32. The first portion 31 contains Al y1 Ga 1-y1 N (0 < y1 ≤ 1). The second portion 32 contains Al y2 Ga 1-y2 N (0 ≤ y2 < 1, y2 < y1). The second portion 32 is between the first portion 31 and at least a part of the second electrode portion 52b. The composition ratio y1 may be, for example, 0.15 or more and 0.8 or less. The composition ratio y2 may be, for example, 0 or more and less than 0.15.

[0023] The current flowing between the first electrode 51 and the second electrode 52 can be controlled by the potential of the third electrode 53. The potential of the third electrode 53 may be, for example, a potential based on the potential of the first electrode 51. The first electrode 51 functions as, for example, a source electrode. The second electrode 52 functions as, for example, a drain electrode. The third electrode 53 functions as, for example, a gate electrode. The semiconductor device 110 is, for example, a transistor.

[0024] The first semiconductor layer 10 includes a portion facing the second semiconductor layer 20. A carrier region 10c is formed in this portion. The carrier region 10c is, for example, a two-dimensional electron gas. The semiconductor device 110 is, for example, a HEMT (High Electron Mobility Transistor).

[0025] For example, the distance along the first direction D1 between the first electrode 51 and the third electrode 53 is shorter than the distance along the first direction D1 between the third electrode 53 and the second electrode 52. This makes it easier to obtain stable operation.

[0026] As described above, in the embodiment, the second electrode 52 is provided with the first electrode portion 52a and the second electrode portion 52b. For example, the first electrode portion 52a may be in contact with the second semiconductor layer 20. The position of the second electrode portion 52b in the first direction D1 is between the position of the third electrode 53 in the first direction D1 and the position of the first electrode portion 52a in the first direction D1. For example, the third semiconductor layer 30 is provided below at least a portion of the second electrode portion 52b. The direction from the third semiconductor layer 30 to the first electrode portion 52a is along the first direction D1. The second electrode portion 52b is, for example, an overhanging portion.

[0027] As described above, the third semiconductor layer 30 is provided between the third semiconductor portion 23 and the second electrode portion 52b. The third semiconductor layer 30 includes a first portion 31 having a high Al composition ratio and a second portion 32 having a low Al composition ratio. For example, the first portion 31 is a portion that contacts the third semiconductor portion 23. The second portion 32 is a portion that contacts the second electrode portion 52b.

[0028] In the embodiment, the electric field is alleviated by providing the third semiconductor layer 30 between the third semiconductor portion 23 and the second electrode portion 52b, which makes it easier to obtain a high breakdown voltage.

[0029] In the first reference example, an insulating layer is provided between the third semiconductor portion 23 and the second electrode portion 52b. In this case, the electric field is also alleviated. However, in the first reference example, carrier traps are easily formed in the insulating layer. Carriers accumulated in the traps are fixed, which tends to make the operation unstable. For example, the on-resistance tends to increase during operation.

[0030] In the embodiment, a semiconductor layer (third semiconductor layer 30) is provided between the third semiconductor portion 23 and the second electrode portion 52b. For example, even if the semiconductor layer (third semiconductor layer 30) includes traps, carriers captured in the traps can move. This suppresses operational instability. For example, it is possible to suppress an increase in on-resistance during operation. In the embodiment, it is possible to provide a semiconductor device that can stabilize characteristics.

[0031] In the second reference example, a p-type or n-type semiconductor layer is provided between the third semiconductor portion 23 and the second electrode portion 52b. The electric field is also reduced in the second reference example. However, p-type or n-type impurities contained in this semiconductor layer may diffuse to other regions, destabilizing the characteristics.

[0032] In contrast, in the embodiment, the third semiconductor layer 30 between the third semiconductor portion 23 and the second electrode portion 52b does not need to contain p-type or n-type impurities, which can prevent the characteristics from becoming unstable due to the diffusion of impurities.

[0033] For example, in the embodiment, the concentration of Mg in the third semiconductor layer 30 is 1×10 17 cm -3 The concentration of Si in the third semiconductor layer 30 is 1×10 17 cm -3 The following is sufficient. Mg acts as a p-type impurity. Si acts as an n-type impurity.

[0034] In the embodiment, the Al composition ratio changes in the third semiconductor layer 30. This causes, for example, charges to be generated. The generation of charges is considered to be based on, for example, polarization. The polarization is based on the change in the composition ratio. Charges may be generated at positions where the composition ratio changes and fixed at those positions. The charges may be, for example, holes.

[0035] FIG. 3 is a schematic view illustrating the semiconductor device according to the first embodiment. 3 illustrates an example of the profile of the Al concentration in the semiconductor member 10M. The horizontal axis of Fig. 3 represents the position pZ in the Z-axis direction, and the vertical axis represents the Al composition ratio C(Al).

[0036] 3, the composition ratio C(Al) is low in the first semiconductor layer 10. The composition ratio C(Al) in the second semiconductor layer 20 is higher than the composition ratio C(Al) in the first semiconductor layer 10. In the third semiconductor layer 30, the composition ratio C(Al) in the first portion 31 is higher than the composition ratio C(Al) in the second portion 32.

[0037] In this example, the Al composition ratio C(Al) in the third semiconductor layer 30 decreases along the direction from the third semiconductor portion 23 to at least a part of the second electrode portion 52b. The third semiconductor layer 30 is a compositionally graded layer.

[0038] In this example, the Al composition ratio y1 in the first portion 31 is equal to or greater than the Al composition ratio x2 in the second semiconductor layer 20. The composition ratio y1 may be higher than the composition ratio x2. For example, more charges can be obtained in the third semiconductor layer 30.

[0039] In the embodiment, the thickness t30 (see FIG. 3) of the third semiconductor layer 30 in the second direction D2 is, for example, 100 nm or more and 400 nm or less. The thickness t31 of the first portion 31 in the second direction D2 may be, for example, 1 nm or more and 10 nm or less. The thickness t32 of the second portion 32 in the second direction D2 may be, for example, 1 nm or more and 10 nm or less.

[0040] In the embodiment, the thickness t10 of the first semiconductor layer 10 in the second direction D2 may be, for example, 100 nm or more and 2000 nm or less, and the thickness t20 of the second semiconductor layer 20 in the second direction D2 may be, for example, 10 nm or more and 100 nm or less.

[0041] 1 and 3, the third semiconductor layer 30 may further include a third portion 33. The third portion 33 is provided between the first portion 31 and the second portion 32. The third portion 33 is made of Al y3 Ga1-y3 It includes N(0 < y3 < 1, y2 < y3 < y1).

[0042] As shown in FIG. 1, the semiconductor device 110 may further include a substrate 18s and a nitride layer 18b. The substrate 18s may be, for example, a silicon substrate. The nitride layer 18b contains Al, Ga, and N. The nitride layer 18b includes, for example, an AlGaN layer. The nitride layer 18b is provided between the substrate 18s and the semiconductor member 10M. The nitride layer 18b is, for example, a buffer layer.

[0043] As shown in FIG. 1, in this example, the semiconductor device 110 further includes an intermediate nitride layer 17. The intermediate nitride layer 17 is provided between the nitride layer 18b and the first semiconductor layer 10. The intermediate nitride layer 17 contains Ga and N. The intermediate nitride layer 17 contains carbon. The concentration of carbon in the intermediate nitride layer 17 is higher than the concentration of carbon in the first semiconductor layer 10. For example, the first semiconductor layer 10 does not contain carbon. The intermediate nitride layer 17 makes it easier to obtain, for example, high crystallinity. The intermediate nitride layer 17 makes it easier to obtain, for example, a high breakdown voltage.

[0044] In this example, the third electrode 53 includes a third electrode portion 53c and a fourth electrode portion 53d. The fourth electrode portion 53d is connected to the third electrode portion 53c. The position of the fourth electrode portion 53d in the first direction D1 is between the position of the third electrode portion 53c in the first direction D1 and the position of the second electrode portion 52b in the first direction D1. The position of at least a part of the third electrode portion 53c in the second direction D2 is between the position of the first semiconductor layer 10 in the second direction D2 and the position of the fourth electrode portion 53d in the second direction D2. The fourth electrode portion 53d is, for example, a flap portion.

[0045] In this example, the first electrode 51 includes a fifth electrode portion 51e and a sixth electrode portion 51f. The sixth electrode portion 51f is connected to the fifth electrode portion 51e. The position of the sixth electrode portion 51f in the first direction D1 is between the position of the fifth electrode portion 51e in the first direction D1 and the position of the third electrode 53 in the first direction D1. The position of at least a part of the fifth electrode portion 51e in the second direction D2 is between the position of the first semiconductor layer 10 in the second direction D2 and the position of the sixth electrode portion 51f in the second direction D2. The sixth electrode portion 51f is, for example, an overhanging portion.

[0046] 2, the first electrode 51, the second electrode 52, and the third electrode 53 may extend along a third direction D3. The third direction D3 intersects with a plane including the first direction D1 and the second direction D2. The third direction D3 is, for example, the Y-axis direction.

[0047] For example, the first electrode portion 52a, the second electrode portion 52b, the third electrode portion 53c, the fourth electrode portion 53d, the fifth electrode portion 51e, and the sixth electrode portion 51f may extend along the third direction D3.

[0048] As shown in FIG. 1, the semiconductor device 110 may further include a first insulating member 41. In this example, the first insulating member 41 includes a first insulating film 41a and a second insulating film 41b. The first insulating film 41a is located between the second semiconductor layer 20 and the second insulating film 41b. In one example, the first insulating film 41a contains silicon and nitrogen. The first insulating film 41a protects, for example, the second semiconductor layer 20. In one example, the second insulating film 41b contains silicon and oxygen. The second insulating film 41b, for example, prevents impurities (such as water) from entering from the outside.

[0049] 1, in this example, at least a portion of the first insulating member 41 (for example, a first insulating film 41a) is provided between the third partial region 13 and the third electrode 53. At least a portion of the first insulating member 41 functions as, for example, a gate insulating film.

[0050] Hereinafter, several examples of the Al composition ratio in the third semiconductor layer 30 will be described.

[0051] FIG. 4 is a schematic view illustrating the semiconductor device according to the first embodiment. The horizontal axis in FIG. 4 represents the position pZ in the Z-axis direction. The vertical axis represents the Al composition ratio C(Al). As shown in FIG. 4, in the semiconductor device 110a according to the embodiment, the third semiconductor layer 30 includes a first portion 31, a second portion 32, and a third portion 33. The thickness t33 of the third portion 33 in the second direction D2 may be, for example, 1 nm or more and 10 nm or less. Except for the above, the configuration of the semiconductor device 110a may be the same as the configuration of the semiconductor device 110.

[0052] FIG. 5 is a schematic view illustrating the semiconductor device according to the first embodiment. The horizontal axis of FIG. 5 represents the position pZ in the Z-axis direction. The vertical axis represents the Al composition ratio C(Al). As shown in FIG. 5, in the semiconductor device 110b according to the embodiment, the third semiconductor layer 30 includes a plurality of portions 30p. The first portion 31, the second portion 32, the third portion 33, etc. may be part of the plurality of portions 30p. Except for the above, the configuration of the semiconductor device 110b may be the same as the configuration of the semiconductor device 110.

[0053] The plurality of portions 30p are aligned along the second direction D2 (Z-axis direction). The Al composition ratio in the plurality of portions 30p is substantially constant. The thickness t30p in the second direction of each of the plurality of portions 30p is 10 nm or less. The thickness t30p may be 1 nm or more.

[0054] In the examples of the semiconductor device 110, the semiconductor device 110a, and the semiconductor device 110b, charges (e.g., holes) are generated at positions in the Z-axis direction where the Al composition ratio C(Al) changes. The short distance between multiple positions where the composition ratio C(Al) changes increases the concentration of the generated charges (holes). This allows carriers captured in the traps to move more easily. Alternatively, the captured carriers are neutralized. This more effectively prevents carriers from accumulating during operation, resulting in fluctuations in characteristics.

[0055] For example, by setting the thickness t30p of each of the portions 30p in the second direction to 10 nm or less, the distance between the positions where the composition ratio C(Al) changes is effectively shortened, and fluctuations in characteristics can be more effectively suppressed.

[0056] FIG. 6 is a schematic view illustrating the semiconductor device according to the first embodiment. The horizontal axis in FIG. 6 represents the position pZ in the Z-axis direction. The vertical axis represents the Al composition ratio C(Al). As shown in FIG. 6, in the semiconductor device 110c according to the embodiment, the Al composition ratio C(Al) in the third semiconductor layer 30 changes continuously. Except for the above, the configuration of the semiconductor device 110c may be similar to that of the semiconductor device 110. In the semiconductor device 110c, the Al composition ratio C(Al) monotonically decreases along the direction from the third semiconductor portion 23 toward at least a part of the second electrode portion 52b. The Al composition ratio C(Al) may change linearly or curvedly. The semiconductor device 110c also provides a semiconductor device with stable characteristics.

[0057] 7 and 8 are schematic cross-sectional views illustrating the semiconductor device according to the first embodiment. 7 and 8 are cross-sectional views corresponding to the cross section taken along line A1-A2 in FIG.

[0058] 7, in the semiconductor device 111 according to the embodiment, at least a portion of the first insulating member 41 is located between the third semiconductor layer 30 and the second electrode portion 52b in the second direction D2. The remaining configuration of the semiconductor device 111 may be similar to that of the semiconductor device 110 (and the semiconductor devices 110a to 110c). In the semiconductor device 111, at least a portion of the first insulating film 41a is located between a portion of the third semiconductor layer 30 and the second electrode portion 52b in the second direction D2.

[0059] 8, in the semiconductor device 111a according to the embodiment, at least a portion of the first insulating member 41 is located between the third semiconductor layer 30 and the second electrode portion 52b in the second direction D2. The remaining configuration of the semiconductor device 111a may be similar to that of the semiconductor device 110 (and the semiconductor devices 110a to 110c). In the semiconductor device 111a, at least a portion of the first insulating film 41a is located between the entire third semiconductor layer 30 and the second electrode portion 52b in the second direction D2. By having at least a portion of the first insulating film 41a cover the entire third semiconductor layer 30 in the second direction D2, it becomes easier to maintain a high concentration of charges (e.g., holes), for example.

[0060] 9(a) to 9(c) are schematic views illustrating the semiconductor device according to the first embodiment. Fig. 9(a) is a plan view, Fig. 9(b) is a cross-sectional view taken along line Y1-Y2 in Fig. 9(a), and Fig. 9(c) is a cross-sectional view taken along line Y3-Y4 in Fig. 9(a).

[0061] 9(a), in the semiconductor device 112 according to the embodiment, the semiconductor member 10M includes a plurality of the third semiconductor layers 30. The configuration of the semiconductor device 112 other than this may be similar to the configuration of the semiconductor device 110 (and the semiconductor devices 110a to 110c).

[0062] The multiple third semiconductor layers 30 are arranged, for example, along a third direction D3 (for example, the Y-axis direction). The third direction D3 intersects with a plane including the first direction D1 and the second direction D2. The direction from one of the multiple third semiconductor layers 30 to another of the multiple third semiconductor layers 30 is along the third direction D3.

[0063] As shown in FIG. 9(b), each of the multiple third semiconductor layers 30 is provided between the third semiconductor portion 23 and the second electrode portion 52b in the second direction D2.

[0064] 9(a), at least a portion of the first insulating member 41 is located in the third direction between one of the plurality of third semiconductor layers 30 and another of the plurality of third semiconductor layers 30. As shown in FIG. 9(c), at least a portion of the first insulating member 41 is provided between the third semiconductor portion 23 and the second electrode portion 52b.

[0065] In the semiconductor device 112, the island-shaped third semiconductor layers 30 and parts of the first insulating members 41 are arranged alternately in the third direction D3.

[0066] For example, by providing the third semiconductor layer 30 including the second portion 32 with a low Al composition ratio, the carrier region 10c (two-dimensional electron gas) is less likely to be formed. If the third semiconductor layer 30 is strip-shaped extending along the third direction D3, the on-resistance may increase excessively. For example, by providing a plurality of island-shaped third semiconductor layers 30, the carrier region 10c is properly formed, and an excessive increase in the on-resistance can be suppressed.

[0067] 10(a) to 10(c) are schematic views illustrating the semiconductor device according to the first embodiment. Fig. 10(a) is a plan view, Fig. 10(b) is a cross-sectional view taken along line Y1-Y2 in Fig. 10(a), and Fig. 10(c) is a cross-sectional view taken along line Y3-Y4 in Fig. 10(a).

[0068] 10(a), in the semiconductor device 112a according to the embodiment, the semiconductor member 10M also includes a plurality of the third semiconductor layers 30. Except for this, the configuration of the semiconductor device 112a may be similar to the configuration of the semiconductor device 112.

[0069] 10(a), in the semiconductor device 112a, the length of one of the multiple third semiconductor layers 30 in the first direction D1 is longer than the length of one of the multiple third semiconductor layers 30 in the third direction D3. Each of the multiple third semiconductor layers 30 may be striped. A portion of each of the multiple third semiconductor layers 30 may not overlap with the second electrode portion 52b in the second direction D2.

[0070] FIG. 11 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. 11, the semiconductor device 113 according to the embodiment further includes a first conductive member 61. The remaining configuration of the semiconductor device 113 may be similar to the configurations of the semiconductor devices 110, 110a to 110c, 111, 111a, 112, and 112a.

[0071] The first conductive member 61 is electrically connected to the first electrode 51. In this example, the first conductive member 61 is electrically connected to the first electrode 51 by a connection member 61L. The position of the first conductive member 61 in the first direction D1 is between the position of the third electrode 53 in the first direction D1 and the position of the second electrode 52 in the first direction D1. For example, the first conductive member 61 functions as a source field plate. By providing the first conductive member 61, the electric field is alleviated, making it easier to obtain a high withstand voltage.

[0072] The semiconductor device 113 may further include a second conductive member 62. The second conductive member 62 is electrically connected to the first electrode 51. For example, at least a portion of the third electrode 53 is provided between the semiconductor member 10M and the second conductive member 62 in the second direction D2. The second conductive member 62 functions as a source field plate. By providing the second conductive member 62, the electric field is alleviated, making it easier to obtain a high withstand voltage.

[0073] The semiconductor device 113 may further include a third conductive member 63. The third conductive member 63 is electrically connected to the second electrode 52. The second electrode portion 52b is provided between the semiconductor member 10M and the third conductive member 63 in the second direction D2. The semiconductor device 113 may further include a second insulating member 42. At least a portion of the second insulating member 42 is provided between the second electrode portion 52b and the third conductive member 63 in the second direction D2. The third conductive member 63 functions as, for example, a drain wiring. The provision of the third conductive member 63 reduces resistance, making it easier to achieve a low on-resistance.

[0074] The second insulating member 42 includes, for example, a third insulating film 42c and a fourth insulating film 42d. The third insulating film 42c is located between the first insulating member 41 and the fourth insulating film 42d. In one example, the third insulating film 42c and the fourth insulating film 42d include silicon and oxygen.

[0075] FIG. 12 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. 12, the semiconductor device 114 according to the embodiment further includes a first conductive member 61. The remaining configuration of the semiconductor device 114 may be the same as that of the semiconductor device 113.

[0076] A part of the third semiconductor layer 30 is provided between the second semiconductor portion 22 and the first conductive member 61. The Al composition ratio in the part of the third semiconductor layer 30 decreases along the direction from the second semiconductor layer 20 to the first conductive member 61. At least a part of the first insulating member 41 may be provided between the part of the third semiconductor layer 30 and the first conductive member 61.

[0077] For example, the first conductive member 61 functions as a source field plate. The third semiconductor layer 30, in which the Al composition ratio changes, is provided between the second semiconductor portion 22 and the first conductive member 61. This reduces the electric field and suppresses fluctuations in characteristics.

[0078] FIG. 13 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. 13, in the semiconductor device 115 according to the embodiment, a part of the third semiconductor layer 30 is provided between the second semiconductor layer 20 and the fourth electrode portion 53d. Except for this, the configuration of the semiconductor device 115 may be the same as the configuration of the semiconductor device 113.

[0079] In the semiconductor device 115, the third electrode 53 includes a third electrode portion 53c and a fourth electrode portion 53d. The fourth electrode portion 53d is connected to the third electrode portion 53c. The position of the fourth electrode portion 53d in the first direction D1 is between the position of the third electrode portion 53c in the first direction D1 and the position of the second electrode portion 52b in the first direction D1. A portion of the third semiconductor layer 30 is provided between the second semiconductor portion 22 and the fourth electrode portion 53d. The Al composition ratio in the portion of the third semiconductor layer 30 decreases in the direction from the second semiconductor portion 22 to the fourth electrode portion 53d. At least a portion of the first insulating member 41 may be provided between the portion of the third semiconductor layer 30 and the fourth electrode portion 53d.

[0080] In the semiconductor device 115, the electric field at the position overlapping with the fourth electrode portion 53d is alleviated, making it easier to obtain a high breakdown voltage. By providing a part of the third semiconductor layer 30 in which the Al composition ratio changes between the second semiconductor portion 22 and the fourth electrode portion 53d, for example, an increase in on-resistance during operation is suppressed.

[0081] FIG. 14 is a schematic cross-sectional view illustrating the semiconductor device according to the first embodiment. 14 , in the semiconductor device 116 according to the embodiment, at least a portion of the third electrode 53 is provided in the first direction between the first semiconductor portion 21 and the second semiconductor portion 22. Except for this, the configuration of the semiconductor device 116 may be similar to the configuration of the semiconductor device 115.

[0082] In the semiconductor device 116, the third electrode 53 is, for example, a recessed gate electrode, which makes it easier to obtain a high threshold voltage, for example, a normally-off operation.

[0083] At least a portion of the third electrode 53 may be provided between the fourth partial region 14 and the fifth partial region 15 in the first direction. As shown in FIG. 14 , at least a portion of the first insulating member 41 may be provided between the first semiconductor layer 10 and the third electrode 53, and between the second semiconductor layer 20 and the third electrode 53.

[0084] In the semiconductor device 116, the third semiconductor layer 30 provided between the second semiconductor portion 22 and the fourth electrode portion 53d may be omitted.

[0085] (Second Embodiment) The second embodiment relates to a method of manufacturing a semiconductor device. FIGS. 15(a) to 15(c) are schematic cross-sectional views illustrating a method of manufacturing a semiconductor device according to the second embodiment. As shown in FIG. 15(a), a third semiconductor layer 30 is formed on the second semiconductor layer 20 provided on the first semiconductor layer 10. The first semiconductor layer 10 is Al x1 Ga 1-x1 N (0 ≦ x1 < 1). The second semiconductor layer 20 is Al x2 Ga 1-x2 N (0 < x2 < 1, x1 < x2). The third semiconductor layer 30 contains Al, Ga, and N. The third semiconductor layer 30 is Al y1 Ga 1-y1 N (0 < y1 ≦ 1) and a first portion 31, and Al y2 Ga 1-y2 N (0 ≦ y2 < 1, y2 < y1) and a second portion 32. The first portion 31 is between the second semiconductor layer 20 and the second portion 32.

[0086] The second direction D2 from the first semiconductor layer 10 to the second semiconductor layer 20 is along the Z-axis direction. The composition ratio of Al in the third semiconductor layer 30 may decrease in the Z-axis direction in a direction away from the second semiconductor layer 20. The third semiconductor layer 30 may be, for example, a composition gradient layer in which the composition ratio of Al changes.

[0087] As shown in FIG. 15(b), a part of the third semiconductor layer 30 is removed to expose a part of the second semiconductor layer 20.

[0088] As shown in FIG. 15(c), an electrode (e.g., the second electrode 52) is formed on at least a part of the above-mentioned part of the exposed second semiconductor layer 20 and on the remaining third semiconductor layer 30. The electrode formed on at least a part of the above-mentioned part of the exposed second semiconductor layer 20 corresponds to the first electrode portion 52a. The electrode formed on the remaining third semiconductor layer 30 corresponds to the second electrode portion 52b. A method of manufacturing a semiconductor device capable of stabilizing characteristics can be provided.

[0089] FIGS. 16(a) and 16(b) are schematic cross-sectional views illustrating a method of manufacturing a semiconductor device according to the second embodiment. As shown in FIG. 16(a), a third semiconductor layer 30 is formed on a part of the second semiconductor layer 20 provided on the first semiconductor layer 10. The first semiconductor layer 10 contains Al x1 Ga 1-x1 N (0 ≦ x1 < 1). The second semiconductor layer 20 contains Al x2 Ga 1-x2 N (0 < x2 < 1, x1 < x2). The third semiconductor layer 30 contains Al, Ga, and N. The third semiconductor layer 30 includes a first portion 31 containing Al y1 Ga 1-y1 N (0 < y1 ≦ 1) and a second portion 32 containing Al y2 Ga 1-y2 N (0 ≦ y2 < 1, y2 < y1). The first portion 31 is between the second semiconductor layer 20 and the second portion 32.

[0090] For example, a mask including an opening is formed on the second semiconductor layer 20. In the opening, the third semiconductor layer 30 is formed on the second semiconductor layer 20. The third semiconductor layer 30 is formed on a part of the second semiconductor layer 20.

[0091] <​​​​16(b), an electrode (e.g., second electrode 52) is formed on another portion of the second semiconductor layer 20 and on the third semiconductor layer 30. The electrode formed on the other portion of the second semiconductor layer 20 corresponds to the first electrode portion 52a. The electrode formed on the third semiconductor layer 30 corresponds to the second electrode portion 52b. A method for manufacturing a semiconductor device capable of stabilizing characteristics can be provided.

[0093] Information about length and thickness can be obtained by electron microscope observation, etc. Information about the material composition can be obtained by SIMS (Secondary Ion Mass Spectrometry) or EDX (Energy Dispersive X-ray spectroscopy), etc.

[0094] The embodiments may include the following technical solutions. (Technical proposal 1) A first electrode; a second electrode, the direction from the first electrode to the second electrode being along a first direction, the second electrode including a first electrode portion and a second electrode portion, the second electrode portion being connected to the first electrode portion; a third electrode, the position of the third electrode in the first direction being between the position of the first electrode in the first direction and the position of the second electrode in the first direction; A semiconductor member; Equipped with The semiconductor member is Al x1 Ga 1-x1A first semiconductor layer containing N(0≦x1<1), wherein the first semiconductor layer includes a first partial region, a second partial region, a third partial region, a fourth partial region, a fifth partial region, and a sixth partial region, the second direction from the first partial region to the first electrode intersects the first direction, the direction from the second partial region to the first electrode portion is along the second direction, the direction from the sixth partial region to the second electrode portion is along the second direction, the direction from the third partial region to the third electrode is along the second direction, the position of the fourth partial region in the first direction is between the position of the first partial region in the first direction and the position of the third partial region in the first direction, the position of the fifth partial region in the first direction is between the position of the third partial region in the first direction and the position of the second partial region in the first direction, and the position of the sixth partial region in the first direction is between the position of the fifth partial region in the first direction and the position of the second partial region in the first direction; the first semiconductor layer Al x2 Ga 1-x2 A second semiconductor layer containing N(0<x2<1, x1<x2), wherein the second semiconductor layer includes a first semiconductor portion, a second semiconductor portion, and a third semiconductor portion, the direction from the fourth partial region to the first semiconductor portion is along the second direction, the direction from the fifth partial region to the second semiconductor portion is along the second direction, and the direction from the sixth partial region to the third semiconductor portion is along the second direction; the second semiconductor layer A third semiconductor layer containing Al, Ga, and N, at least a part of the third semiconductor layer is provided between the third semiconductor portion and at least a part of the second electrode portion in the second direction, and the third semiconductor layer contains Al y1 Ga 1-y1 A first part containing N(0<y1≦1), and Al y2 Ga 1-y2 A second part containing N(0≦y2<1, y2<y1), and the second part is between the first part and at least a part of the second electrode portion; the third semiconductor layer A semiconductor device including

[0095] (Technical Solution 2) The semiconductor device according to Technical Solution 1, wherein y1 is not less than x2.

[0096] <000\0436>(Technical Solution 3) The semiconductor device according to Technical Solution 1, wherein y1 is higher than x2.

[0097] (Technical Solution 4) The third semiconductor layer further includes a third portion provided between the first portion and the second portion, The third portion is Al y3 Ga 1-y3 N (0 < y3 < 1, y2 < y3 < y1), and the semiconductor device according to any one of Technical Solutions 1 to 3.

[0098] (Technical Solution 5) The semiconductor device according to any one of Technical Solutions 1 to 4, wherein the composition ratio of Al in the third semiconductor layer decreases along the direction from the third semiconductor portion to at least a part of the second electrode portion.

[0099] [[ID=##]] (Technical Solution 6) The third semiconductor layer includes a plurality of portions arranged along the second direction, The composition ratio of Al in the plurality of portions is substantially constant, The thickness of each of the plurality of portions in the second direction is 10 nm or less, and the semiconductor device according to Technical Solution 5.

[0100] (Technical Solution 7) The concentration of Mg in the third semiconductor layer is 1 × 10 17 cm -3 or less, and the semiconductor device according to any one of Technical Solutions 1 to 6.

[0101] (Technical Solution 8) The thickness of the third semiconductor layer in the second direction is 100 nm or more and 400 nm or less, and the semiconductor device according to any one of Technical Solutions 1 to 7.

[0102] (Technical Solution 9) Further comprising a first insulating member; The semiconductor device according to any one of Technical Solutions 1 to 8, wherein at least a portion of the first insulating member is located between the third semiconductor layer and the second electrode portion in the second direction.

[0103] (Technical proposal 10) Further comprising a first insulating member; the semiconductor member includes a plurality of the third semiconductor layers, a direction from one of the plurality of third semiconductor layers to another of the plurality of third semiconductor layers is along a third direction intersecting a plane including the first direction and the second direction; at least a portion of the first insulating member is located between the one of the plurality of third semiconductor layers and the other of the plurality of third semiconductor layers in the third direction; The semiconductor device according to any one of Technical Solutions 1 to 8, wherein the at least a portion of the first insulating member is provided between the third semiconductor portion and the second electrode portion.

[0104] (Technical proposal 11) a first conductive member electrically connected to the first electrode; a position of the first conductive member in the first direction is between the position of the third electrode in the first direction and the position of the second electrode in the first direction; a portion of the third semiconductor layer is provided between the second semiconductor portion and the first conductive member; The semiconductor device according to any one of Technical Solutions 1 to 8, wherein the Al composition ratio in the portion of the third semiconductor layer decreases along a direction from the second semiconductor layer to the first conductive member.

[0105] (Technical proposal 12) the third electrode includes a third electrode portion and a fourth electrode portion; the fourth electrode portion is connected to the third electrode portion, a position of the fourth electrode portion in the first direction is between a position of the third electrode portion in the first direction and a position of the second electrode portion in the first direction; a portion of the third semiconductor layer is provided between the second semiconductor portion and the fourth electrode portion; The semiconductor device according to any one of Technical Schemes 1 to 8, wherein the Al composition ratio in the portion of the third semiconductor layer decreases along a direction from the second semiconductor portion to the fourth electrode portion.

[0106] (Technical proposal 13) Further comprising a first insulating member; at least a portion of the third electrode is provided between the first semiconductor portion and the second semiconductor portion in the first direction; A semiconductor device described in Technical Proposal 12, wherein at least a portion of the first insulating member is provided between the first semiconductor layer and the third electrode, and between the second semiconductor layer and the third electrode.

[0107] (Technical proposal 14) Further comprising a first insulating member; at least a portion of the third electrode is provided between the first semiconductor portion and the second semiconductor portion in the first direction; A semiconductor device described in any one of technical proposals 1 to 8, wherein at least a portion of the first insulating member is provided between the first semiconductor layer and the third electrode, and between the second semiconductor layer and the third electrode.

[0108] (Technical proposal 15) a second conductive member electrically connected to the first electrode; The semiconductor device according to any one of Technical Solutions 1 to 14, wherein at least a portion of the third electrode is provided between the semiconductor member and the second conductive member in the second direction.

[0109] (Technical proposal 16) a third conductive member electrically connected to the second electrode; A second insulating member; the second electrode portion is provided between the semiconductor member and the third conductive member in the second direction, At least a part of the second insulating member is provided between the second electrode portion and the third conductive member in the second direction, and the semiconductor device according to any one of Technical Schemes 1 to 15.

[0110] (Technical Scheme 17) The second electrode portion extends along a third direction intersecting a plane including the first direction and the second direction, and the semiconductor device according to any one of Technical Schemes 1 to 9.

[0111] (Technical Scheme 18) x1 is 0 or more and less than 0.15, x2 is 0.15 or more and 0.4 or less, y1 is 0.15 or more and 0.8 or less, y2 is 0 or more and less than 0.15, and the semiconductor device according to any one of Technical Schemes 1 to 17.

[0112] (Technical Scheme 19) Al x1 Ga 1-x1 Provided on a first semiconductor layer containing Al, Ga, N (0 ≦ x1 < 1), Al x2 Ga 1-x2 Form a third semiconductor layer containing Al, Ga, and N on a second semiconductor layer containing Al, Ga, N (0 < x2 < 1, x1 < x2), and the third semiconductor layer is Al y1 Ga 1-y1 A first portion containing Al, Ga, N (0 < y1 ≦ 1), and Al y2 Ga 1-y2 A second portion containing Al, Ga, N (0 ≦ y2 < 1, y2 < y1), and the first portion is between the second semiconductor layer and the second portion. Remove a part of the third semiconductor layer to expose a part of the second semiconductor layer. Form an electrode on at least a part of the exposed part of the second semiconductor layer and on the remaining third semiconductor layer, and a method for manufacturing a semiconductor device.

[0113] (Technical Scheme 20) Al x1 Ga 1-x1 Provided on a first semiconductor layer containing Al, Ga, N (0 ≦ x1 < 1), Alx2 Ga 1-x2 Form a third semiconductor layer containing Al, Ga, and N on a part of a second semiconductor layer containing N(0 < x2 < 1, x1 < x2), and the third semiconductor layer contains Al y1 Ga 1-y1 A first portion containing N(0 < y1 ≦ 1), and Al y2 Ga 1-y2 A second portion containing N(0 ≦ y2 < 1, y2 < y1), and the first portion is between the part of the second semiconductor layer and the second portion A method of manufacturing a semiconductor device, comprising forming electrodes on another part of the second semiconductor layer and on the third semiconductor layer

[0114] According to an embodiment, a semiconductor device capable of stabilizing characteristics and a method of manufacturing the same are provided

[0115] As described above, embodiments of the present invention have been described with reference to examples. However, the present invention is not limited to these examples. For example, with respect to the specific configurations of each element such as electrodes, semiconductor regions, and insulating members included in the semiconductor device, those skilled in the art can appropriately select from the known range to implement the present invention in the same manner and obtain the same effects as long as they are included in the scope of the present invention

[0116] Combinations of any two or more elements of each example within a technically possible range are also included in the scope of the present invention as long as they include the gist of the present invention

[0117] Based on the semiconductor device and its manufacturing method described above as embodiments of the present invention, all semiconductor devices and their manufacturing methods that those skilled in the art can appropriately design and modify and implement also belong to the scope of the present invention as long as they include the gist of the present invention

[0118] Those skilled in the art can conceive various modification examples and correction examples within the scope of the idea of the present invention, and it is understood that those modification examples and correction examples also belong to the scope of the present invention

[0119] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0120] 10, 20, 30: first, second, third semiconductor layers, 10M: semiconductor member, 10c: carrier region, 11-16: first to sixth partial regions, 17: intermediate nitride layer, 18b: nitride layer, 18s: base, 21-23: first to third semiconductor portions, 30p: portion, 31-33: first to third portions, 41, 42: first and second insulating members, 41a, 41b: first and second insulating films, 42c, 42d: third and fourth insulating films, 51-53: first to third electrodes, 51e, 52f: fifth and sixth electrode portions, 52a, 52b: first and second electrode portions, 53c, 53d: third and fourth electrode portions, 61-63: first to third conductive members, 61L: connecting member; 110, 110a to 110c, 111, 111a, 112, 112a, 113 to 116: semiconductor device; C(Al): composition ratio; D1 to D3: first to third directions; t10, t20, t30, t30p, t31 to t33: thickness

Claims

1. A first electrode; a second electrode, the direction from the first electrode to the second electrode being along a first direction, the second electrode including a first electrode portion and a second electrode portion, the second electrode portion being connected to the first electrode portion; a third electrode, the position of the third electrode in the first direction being between the position of the first electrode in the first direction and the position of the second electrode in the first direction; A semiconductor member; Equipped with The semiconductor member is Al ｘ１ Ga １－ｘ１ a first semiconductor layer including N (0≦x1<1), the first semiconductor layer including a first partial region, a second partial region, a third partial region, a fourth partial region, a fifth partial region, and a sixth partial region, a second direction from the first partial region to the first electrode intersects with the first direction, a direction from the second partial region to the first electrode portion is along the second direction, a direction from the sixth partial region to the second electrode portion is along the second direction, a direction from the third partial region to the third electrode is along the second direction, a position of the fourth partial region in the first direction is between a position of the first partial region in the first direction and a position of the third partial region in the first direction, a position of the fifth partial region in the first direction is between the position of the third partial region in the first direction and a position of the second partial region in the first direction, and a position of the sixth partial region in the first direction is between the position of the fifth partial region in the first direction and the position of the second partial region in the first direction; Al ｘ２ Ga １－ｘ２ N (0<x2<1, x1<x2), the second semiconductor layer including a first semiconductor portion, a second semiconductor portion, and a third semiconductor portion, the direction from the fourth partial region to the first semiconductor portion being along the second direction, the direction from the fifth partial region to the second semiconductor portion being along the second direction, and the direction from the sixth partial region to the third semiconductor portion being along the second direction; a third semiconductor layer containing Al, Ga, and N, at least a portion of the third semiconductor layer being provided between the third semiconductor portion and at least a portion of the second electrode portion in the second direction, and the third semiconductor layer containing Al ｙ１ Ga １－ｙ１ a first portion including N (0<y1≦1); and Al ｙ２ Ga １－ｙ２ N (0≦y2<1, y2<y1), and the second portion is between the first portion and the at least part of the second electrode portion; and a semiconductor device comprising:

2. The semiconductor device according to claim 1 , wherein said y1 is equal to or greater than said x2.

3. The semiconductor device according to claim 1 , wherein said y1 is higher than said x2.

4. 4. The semiconductor device according to claim 1, wherein the Al composition ratio in said third semiconductor layer decreases along a direction from said third semiconductor portion to said at least one part of said second electrode portion.

5. the third semiconductor layer includes a plurality of portions aligned along the second direction, the Al composition ratio in the plurality of portions is substantially constant; The semiconductor device according to claim 4 , wherein the thickness of each of the plurality of portions in the second direction is 10 nm or less.

6. Further comprising a first insulating member; the semiconductor member includes a plurality of the third semiconductor layers, a direction from one of the plurality of third semiconductor layers to another of the plurality of third semiconductor layers is along a third direction intersecting a plane including the first direction and the second direction; at least a portion of the first insulating member is located between the one of the plurality of third semiconductor layers and the other of the plurality of third semiconductor layers in the third direction; The semiconductor device according to claim 1 , wherein the at least a portion of the first insulating member is provided between the third semiconductor portion and the second electrode portion.

7. a first conductive member electrically connected to the first electrode; a position of the first conductive member in the first direction is between the position of the third electrode in the first direction and the position of the second electrode in the first direction; a portion of the third semiconductor layer is provided between the second semiconductor portion and the first conductive member, The semiconductor device according to claim 1 , wherein the Al composition ratio in said portion of said third semiconductor layer decreases along a direction from said second semiconductor layer to said first conductive member.

8. the third electrode includes a third electrode portion and a fourth electrode portion; the fourth electrode portion is connected to the third electrode portion; a position of the fourth electrode portion in the first direction is between a position of the third electrode portion in the first direction and a position of the second electrode portion in the first direction; a portion of the third semiconductor layer is provided between the second semiconductor portion and the fourth electrode portion, The semiconductor device according to claim 1 , wherein the Al composition ratio in said part of said third semiconductor layer decreases along a direction from said second semiconductor portion to said fourth electrode portion.

9. Al ｘ１ Ga １－ｘ１ Al provided on the first semiconductor layer containing N (0≦x1<1). ｘ２ Ga １－ｘ２ A third semiconductor layer containing Al, Ga, and N is formed on a second semiconductor layer containing N (0<x2<1, x1<x2), and the third semiconductor layer is Al ｙ１ Ga １－ｙ１ a first portion including N (0<y1≦1); and Al ｙ２ Ga １－ｙ２ N (0≦y2<1, y2<y1), wherein the first portion is between the second semiconductor layer and the second portion; removing a portion of the third semiconductor layer to expose a portion of the second semiconductor layer; forming an electrode on at least a part of the exposed portion of the second semiconductor layer and on the remaining third semiconductor layer.

10. Al ｘ１ Ga １－ｘ１ Al provided on the first semiconductor layer containing N (0≦x1<1). ｘ２ Ga １－ｘ２ A third semiconductor layer containing Al, Ga, and N is formed on a part of the second semiconductor layer containing N (0<x2<1, x1<x2), and the third semiconductor layer is ｙ１ Ga １－ｙ１ a first portion including N (0<y1≦1); and Al ｙ２ Ga １－ｙ２ N (0≦y2<1, y2<y1), wherein the first portion is between the part of the second semiconductor layer and the second portion; forming electrodes on another portion of the second semiconductor layer and on the third semiconductor layer.

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