Semiconductor device

Abstract

To obtain a HEMT having a PSJ structure with improved switching speed.SOLUTION: A semiconductor device includes: a first nitride semiconductor layer 12; a second nitride semiconductor layer 13 having a wider band gap than that of the first nitride semiconductor layer 12; and a third nitride semiconductor layer 14 having a narrower band gap than that of the second nitride semiconductor layer 13. A drain electrode 22 and a source electrode 21 are not in direct contact with the third nitride semiconductor layer 14 and are formed on the first nitride semiconductor layer 12. A gate electrode 24 is formed on the third nitride semiconductor layer 14 between a drain electrode 11 and the source electrode 21. An auxiliary electrode 25 is locally formed on the third nitride semiconductor layer 14 between the gate electrode 24 and the drain electrode 22.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to the structure of a semiconductor device using a heterojunction of nitride semiconductors.

Background Art

[0002] As a semiconductor device using a heterojunction of nitride semiconductors (GaN or its mixed crystal semiconductor), for example, a HEMT (High Electron Mobility Transistor) is known. Such a semiconductor device is required to have a breakdown voltage between the source and drain in the off state. Further, although a current collapse phenomenon is known as a problem in a HEMT using a nitride semiconductor, it is said that it is effective to relax the local electric field concentration between the drain and gate in order to reduce the current collapse phenomenon.

[0003] As an example of a HEMT structure using a nitride semiconductor, there is a PSJ (Polarization Super Junction) structure as described in Patent Document 1. FIG. 8(a) is a cross-sectional view schematically showing the structure of a GaN-HEMT having a PSJ structure, and FIG. 8(b) is a diagram showing the operating principle corresponding thereto. In the semiconductor device 9 shown in FIG. 8(a), for example, a nitride semiconductor layer (first nitride semiconductor layer 12) made of non-doped GaN is epitaxially grown on a substrate 11 made of sapphire. On the first nitride semiconductor layer 12, a nitride semiconductor layer (second nitride semiconductor layer 13) made of non-doped AlGaN (more precisely, Al 1-x Ga x N: 0 <x <1) is formed.

[0004] A nitride semiconductor layer (third nitride semiconductor layer 14) made of undoped GaN similar to that of the first nitride semiconductor layer 12 is formed on the second nitride semiconductor layer 13. A source electrode (second main electrode) 21 and a drain electrode (first main electrode) 22 are connected to both the left and right sides of the second nitride semiconductor layer 13 and on the first nitride semiconductor layer 12, respectively. The third nitride semiconductor layer 14 is formed locally on the second nitride semiconductor layer 13, and an insulating layer 23 made of a silicon oxide film is provided between the third nitride semiconductor layer 14 and the source electrode 21 and drain electrode 22. A gate electrode (control electrode) 24 is formed on the source electrode 21 side of the third nitride semiconductor layer 14, via a nitride semiconductor layer (conductive nitride semiconductor layer 15) made of p-type GaN (p-GaN). The conductive nitride semiconductor layer 15 is provided to form a good pn junction between the gate electrode 24 and the third nitride semiconductor layer 14, which makes it easier to control the on / off state of the channel directly below the gate electrode 24.

[0005] In this structure, in the heterostructure (polarization super junction) consisting of the first nitride semiconductor layer 12, the second nitride semiconductor layer 13, and the third nitride semiconductor layer 14, as shown in FIG. 8( b), spontaneous polarization due to the piezoelectric effect causes a two-dimensional electron gas in which electrons E are accumulated in a planar manner to be formed in the first nitride semiconductor layer 12 near the interface between the first nitride semiconductor layer 12 and the second nitride semiconductor layer 13, and a two-dimensional hole gas in which holes H are accumulated in a planar manner to be formed in the third nitride semiconductor layer 14 near the interface between the second nitride semiconductor layer 13 and the third nitride semiconductor layer 14. In the above structure, in the on-state, the source electrode 21 and the drain electrode 22 are connected by a two-dimensional electron gas channel, and a current flows between them. On the other hand, the upper two-dimensional hole gas is not connected to the source electrode 21 or the drain electrode 22.

[0006] By applying a negative potential to the gate electrode 24, the two-dimensional electron gas immediately below the gate electrode 24 disappears, and the semiconductor device 9 enters an off state. When turned off, electrons E constituting the two-dimensional electron gas move toward the drain electrode 22, and holes H constituting the two-dimensional hole gas move toward the gate electrode 24. This makes the electric field strength in the third nitride semiconductor layer 14 from the gate electrode 24 toward the drain electrode 22 approximately uniform, and reduces local increases in the electric field strength immediately below the gate electrode 24, etc. This allows the withstand voltage of the semiconductor device 9 to be increased. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2023-123161 Summary of the Invention [Problem to be solved by the invention]

[0008] From the viewpoint of breakdown voltage, it is desirable to form the PSJ structure close to the drain electrode 22. However, when a semiconductor device using a PSJ structure such as that shown in Figure 8(b) is turned off, holes H in the two-dimensional hole gas move toward the gate electrode 24, but the mobility (corresponding to speed) of the holes H is small, about one-quarter of the mobility of the electrons E. Even when an off signal is applied to the gate electrode 24, it takes a relatively long time for the holes H present on the drain electrode 22 side to reach the gate electrode 24, making it difficult to increase the switching speed of a HEMT with a PSJ structure.

[0009] The present disclosure has been made in consideration of these problems, and aims to provide an invention that solves the above problems. [Means for solving the problem]

[0010] In order to solve the above problems, the present disclosure has the following configuration. The present disclosure relates to a semiconductor device in which a current flowing between a first main electrode and a second main electrode is controlled by the potential of a control electrode, the semiconductor device comprising: a first nitride semiconductor layer; a second nitride semiconductor layer provided on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer; and a third nitride semiconductor layer provided on a portion of an upper surface of the second nitride semiconductor layer and having a band gap narrower than that of the second nitride semiconductor layer, wherein the first main electrode and the second main electrode are not in direct contact with the third nitride semiconductor layer but are formed on the first nitride semiconductor layer, the control electrode is formed on the third nitride semiconductor layer between the first main electrode and the second main electrode, and an auxiliary electrode is formed locally on the third nitride semiconductor layer between the control electrode and the first main electrode. The present disclosure relates to a semiconductor device in which a current flowing between a first main electrode and a second main electrode is controlled by the potential of a control electrode, the semiconductor device comprising: a first nitride semiconductor layer; a second nitride semiconductor layer provided on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer; and a third nitride semiconductor layer provided on a part of an upper surface of the second nitride semiconductor layer and having a band gap narrower than that of the second nitride semiconductor layer, wherein the first main electrode and the second main electrode are not in direct contact with the third nitride semiconductor layer but are formed on the first nitride semiconductor layer, the control electrode is formed on the third nitride semiconductor layer between the first main electrode and the second main electrode, and an auxiliary electrode is locally formed on the third nitride semiconductor layer between the control electrode and the first main electrode with a p-type fourth nitride semiconductor layer interposed therebetween. The auxiliary electrode and the control electrode may be connected. A potential more positive than that of the second main electrode may be applied to the first main electrode, and when the current is turned off, a potential greater than that of the control electrode and less than that of the first main electrode may be applied to the auxiliary electrode. A field plate electrode may be provided on the second nitride semiconductor layer between the third nitride semiconductor layer and the first main electrode, with an insulating layer interposed therebetween. The field plate electrode and the auxiliary electrode may be connected to each other. In a plan view, the auxiliary electrodes may be arranged in a dispersed manner in a second direction perpendicular to a first direction from the first main electrode toward the second main electrode. [Effects of the Invention]

[0011] Since the present disclosure is configured as described above, it is possible to obtain a PSJ structure HEMT with improved switching speed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating a structure of a semiconductor device according to an embodiment of the present disclosure. [Figure 2] 1A and 1B are diagrams illustrating a schematic diagram of an operation at turn-off in a semiconductor device according to an embodiment of the present disclosure. [Figure 3] 1A and 1B are diagrams illustrating an example of a planar structure of an electrode in a semiconductor device according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a cross-sectional view illustrating a first modified example of the semiconductor device according to the embodiment of the present disclosure. [Figure 5] FIG. 10 is a cross-sectional view showing a second modified example of the semiconductor device according to the embodiment of the present disclosure. [Figure 6] FIG. 10 is a cross-sectional view illustrating a third modified example of the semiconductor device according to the embodiment of the present disclosure. [Figure 7] FIG. 10 is a cross-sectional view illustrating a fourth modified example of the semiconductor device according to the embodiment of the present disclosure. [Figure 8] 1A is a cross-sectional view showing the structure of a conventional PSJ structure HEMT, and FIG. 1B is a schematic view showing the state of the HEMT when it is on. DETAILED DESCRIPTION OF THE INVENTION

[0013] Semiconductor devices according to embodiments of the present disclosure will be described below with reference to the drawings. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between thickness and planar dimensions, the ratio of lengths of each part, and the like may differ from the actual ones. Therefore, specific dimensions should be determined with reference to the following description. Furthermore, it goes without saying that the drawings may include parts with different dimensional relationships and ratios. Furthermore, the embodiments described below exemplify devices that embody the technical ideas of this disclosure, and the technical ideas of this disclosure do not limit the shape, structure, arrangement, etc. of the components to those described below. Various modifications can be made to the embodiments of this disclosure within the scope of the claims. Note that terms specifying top and bottom, such as "top" and "bottom," are used in this disclosure for convenience of description, and even if a component is provided on a side surface, it falls within the scope of the present invention as long as it is substantially the same as the constituent elements of this disclosure. Furthermore, "on" includes not only cases where the material is formed in contact with the object, but also cases where the material is formed via another layer. Furthermore, in this disclosure, "connection" is not limited to direct connection, and even when a connection is made via an intervening resistor or other element, it falls within the scope of the present invention as long as it is substantially the same as the constituent elements of this disclosure.

[0014] The semiconductor device according to the embodiment of the present disclosure is a HEMT with a PSJ structure, similar to the semiconductor device 9. However, a structure is adopted here that shortens the time it takes for the two-dimensional hole gas in the PSJ structure to disappear when switching from the on state to the off state, while still maintaining a relatively high breakdown voltage. This increases the switching speed of the semiconductor device while maintaining a relatively high breakdown voltage.

[0015] 1 is a cross-sectional view of a semiconductor device 1 according to an embodiment of the present disclosure. Here, the semiconductor device 1 includes a substrate 11 made of sapphire, a first nitride semiconductor layer 12 made of undoped GaN, and an undoped Al semiconductor layer 13 having a wider band gap than the first nitride semiconductor layer 12 and containing, for example, Al. x Ga1-x 8(b), a second nitride semiconductor layer 13 made of N (where x>0), a third nitride semiconductor layer 14 having a narrower band gap than the second nitride semiconductor layer 13 and made of, for example, undoped GaN, a source electrode 21, a drain electrode 22, an insulating layer 23, a conductive nitride semiconductor layer 15 made of p-GaN, and a gate electrode 24 are also provided. As in Fig. 8(b), a two-dimensional electron gas layer and a two-dimensional hole gas layer are formed during the on-state.

[0016] The source electrode 21 and the drain electrode 22 are made of a material that makes ohmic contact with the two-dimensional electron gas, for example, a Ti / Au stacked structure. The source electrode 21 and the drain electrode 22 are not in direct contact with the third nitride semiconductor layer, but are formed on the first nitride semiconductor layer 12. In FIG. 1, the source electrode 21 and the drain electrode 22 are in contact with the first nitride semiconductor layer 12, but they may be formed on the second nitride semiconductor layer 13. The gate electrode 24 is made of a material that makes relatively ohmic contact with the conductive nitride semiconductor layer 15, for example, a Ni / Au stacked structure.

[0017] 1, an auxiliary electrode 25 is provided on the third nitride semiconductor layer 14 and is connected to the gate electrode 24. The auxiliary electrode 25 can be made of a material capable of extracting holes H from the third nitride semiconductor layer 14 (GaN), such as a metal structure for a p-type nitride semiconductor such as Ni / Au or a p-type metal oxide semiconductor such as NiO. Since the auxiliary electrode 25 is connected to the gate electrode 24 outside the illustrated range, the potential of the auxiliary electrode 25 is equal to the potential of the gate electrode 24.

[0018] 2(a) to 2(c) schematically show the states of electrons E and holes H in this semiconductor device 1 from on to off. FIG. 2(a) shows the on state in which a potential equal to or greater than the threshold is applied to the gate electrode 24. Holes H exist in the third nitride semiconductor layer 14 in the PSJ structure. Electrons E exist between the source electrode 21 and the drain electrode 22, allowing an operating current to flow.

[0019] 2(b) schematically shows a state in which a negative potential is applied to gate electrode 24 to change from on to off. Electrons E present on the drain electrode 22 side in first nitride semiconductor layer 12 move toward drain electrode 22. Holes H present in third nitride semiconductor layer 14 move toward gate electrode 24 or auxiliary electrode 25 to which a negative potential is applied. In this state, the electron concentration directly below gate electrode 24 is at least lower than in the on state.

[0020] While the potential caused by the movement of holes H prevents the depletion layer from expanding sufficiently to block the current between the drain electrode 22 and the source electrode, the device will not enter the off state even if an off signal is applied to the gate electrode 24. It is necessary to prevent the movement of holes H in the third nitride semiconductor layer 14.

[0021] In this semiconductor device 1, the auxiliary electrode 25 is formed on the third semiconductor layer 14 between the gate electrode 24 and the drain electrode 22. Holes H in the third nitride semiconductor layer 14 flow not only to the gate electrode 24 but also to the auxiliary electrode 25. In particular, holes H present in the third nitride semiconductor layer 14 on the drain electrode 22 side move to the auxiliary electrode 25. Therefore, as shown in FIG. 2(c), holes H in the third nitride semiconductor layer 14 are quickly discharged. This allows the semiconductor device 1 to be quickly turned off.

[0022] In the above configuration, the auxiliary electrode 25 is formed on the third semiconductor layer 14 between the gate electrode 24 and the drain electrode 22, and its position is appropriately set so that holes H can be quickly discharged from the auxiliary electrode 25. In the above example, the gate electrode 24 and the auxiliary electrode 25 are connected and have the same potential, but they do not have to be at the same potential. For example, it is clear that the same effect can be achieved even if the potential applied to the auxiliary electrode 25 during the off state is a negative potential whose absolute value is smaller than the potential (negative) of the gate electrode 24.

[0023] Furthermore, the potential of the auxiliary electrode 25 in this case does not necessarily have to be on the negative side. When it is off, for example, if the potential of the drain electrode 22 is set to (+)VD in FIG. 1, the potential of the semiconductor layer between the source electrode 21 and the drain electrode 22 has a distribution ranging from 0 to VD from the source electrode 21 side to the drain electrode 22 side. Therefore, the potential VK of the semiconductor layer at the location where the auxiliary electrode 25 is formed satisfies 0 < VK < VD, and VK is positive. In this case, if the potential of the auxiliary electrode 25 is lower than VK (i.e., on the negative side), holes H are discharged from the auxiliary electrode 25. Therefore, the potential of the auxiliary electrode 25 can be set on the positive side or, in fact, within a range smaller than VD according to the position where the auxiliary electrode 25 is installed.

[0024] Also, although FIG. 1 shows a cross-section along the direction connecting the source electrode 21 and the drain electrode 22, in reality, the planar shapes of the source electrode 21 and the drain electrode 22 are appropriately set, and the planar shape of the gate electrode 24 is set so that the current path between them can be blocked. In this case, as described above, the auxiliary electrode 25 is provided between the gate electrode 24 and the drain electrode 22, but the auxiliary electrode 25 does not necessarily have to be in a form that blocks the current path between the source electrode 21 and the drain electrode 22. Therefore, the auxiliary electrode 25 can have a planar shape different from that of the gate electrode 24. FIG. 3 is a plan view showing such a configuration example. In FIGS. 3(a) and (b), they extend in a direction perpendicular to the direction in which the source electrode 21, the gate electrode 24, and the drain electrode 22 are arranged (the horizontal direction in FIGS. 1 and 3: the first direction), that is, the direction perpendicular to the paper surface in FIG. 1 and the vertical direction in FIG. 3 (the second direction). On the other hand, in FIG. 3(a), the auxiliary electrodes 25 are spaced apart from each other and arranged in a dispersed manner in this second direction. Also, in FIG. 3(b), the arrangement of the auxiliary electrodes 25 along this second direction is such that there are a plurality of them in the first direction, and they are arranged in a staggered pattern where the auxiliary electrodes 25 alternate with each other. Thereby, the influence on the potential distribution between the gate and the drain due to the provision of the auxiliary electrode 25 can be reduced as much as possible. The planar form of the auxiliary electrode 25 is appropriately set according to the planar shapes of the source electrode 21, the drain electrode 22, and the gate electrode 24.

[0025] A first modification of the semiconductor device 1 will now be described. Fig. 4 is a cross-sectional view showing the structure of such a semiconductor device 2. In the previous example, auxiliary electrode 25 was in contact with third nitride semiconductor layer 14, whereas in this semiconductor device 2, auxiliary electrode 25, like gate electrode 24, is connected to third nitride semiconductor layer 14 via fourth nitride semiconductor layer 16 made of a p-type nitride semiconductor layer such as p-GaN.

[0026] In this case, the same operation as in Fig. 2 can be performed. In this case, the contact resistance between the auxiliary electrode 25 and the third nitride semiconductor layer 14 (two-dimensional hole gas) can be substantially reduced, so that the holes H can be discharged more efficiently from the auxiliary electrode 25, and the switching speed can be further increased.

[0027] Although both the conductive nitride semiconductor layer 15 and the fourth nitride semiconductor layer 16 are p-GaN (p-type GaN), the p-type impurity concentration and the like do not need to be the same. z Al y Ga 1-z-y N (z≧0, 1≧y>x>0: x is the ratio of Al in the second nitride semiconductor layer 13), and z and y may be different between the conductive nitride semiconductor layer 15 and the fourth nitride semiconductor layer 16.

[0028] A second modification will now be described. Fig. 5 is a cross-sectional view showing the structure of such a semiconductor device 3. In this semiconductor device 3, a field plate electrode 26 is provided on an insulating layer 23 provided between the third nitride semiconductor layer 14 and the drain electrode 22, in contrast to the semiconductor device 1 shown in Fig. 1. The insulating layer 23 is formed thicker than the third nitride semiconductor layer 14, and the field plate electrode 26 is formed on the insulating layer 23. The potential of the field plate electrode 26 can be, for example, connected to the gate electrode 24 and set to the same potential, but it does not have to be the same potential. For example, the potential applied to the field plate electrode 26 may be equal to or higher than the potential applied to the gate electrode 24 and lower than the potential applied to the drain electrode 22.

[0029] In this structure, the field plate electrode 26 can mitigate the increase in the electric field near the end of the third nitride semiconductor layer 14 on the drain electrode 22 side. The function of the auxiliary electrode 25 is the same as that described above.

[0030] A third modified example will now be described. Fig. 6 is a cross-sectional view showing the structure of such a semiconductor device 4. In this semiconductor device 4, auxiliary electrode 27 is used, which is an integrated structure of auxiliary electrode 25 and field plate electrode 26 in semiconductor device 3 shown in Fig. 4. As in the second modified example, in this structure as well, field plate electrode 26 can alleviate the increase in the electric field near the end of third nitride semiconductor layer 14 on the drain electrode 22 side.

[0031] A fourth modification will now be described. FIG. 7 is a cross-sectional view showing the structure of such a semiconductor device 5. In this semiconductor device 5, instead of the auxiliary electrode 27 in which the auxiliary electrode 25 and the field plate electrode 26 are integrated in the semiconductor device 3 shown in FIG. 6, the auxiliary electrode 25 and the field plate electrode 28 are separately provided on the third nitride semiconductor layer 14. The auxiliary electrode 25 is provided on the third nitride semiconductor layer 14 between the gate electrode 24 and the drain electrode 22 and is connected to the gate electrode 24 outside the illustrated range. Here, the distance L1 from the gate electrode 24 to the end of the auxiliary electrode 25 on the drain electrode 22 side may be equal to or less than the distance L2 from the end of the auxiliary electrode 25 on the drain electrode 22 side to the end of the third nitride semiconductor layer 14 on the drain electrode 22 side, and more preferably, may be less than the distance L2 from the end of the auxiliary electrode 25 on the drain electrode 22 side to the end of the third nitride semiconductor layer 14 on the drain electrode 22 side. This makes it relatively easy to ensure a sufficient withstand voltage between the drain and gate, and the semiconductor device 5 can be quickly turned off. Field plate electrode 28 is not connected to gate electrode 24, but is connected to the surface of third nitride semiconductor layer 14. It is desirable to provide field plate electrode 28 closer to drain electrode 22 of third nitride semiconductor layer 14 than auxiliary electrode 25. In the structure of the fourth modified example as well, field plate electrode 28 can alleviate the increase in the electric field near the end of third nitride semiconductor layer 14 on the drain electrode 22 side.

[0032] Although the semiconductor device according to the embodiment of the present disclosure and the first to fourth modified examples have been described taking as an example a normally-on operation in which an off signal is applied to gate electrode 24, the present disclosure may also be applied to a semiconductor device in which two-dimensional electron gas is disrupted in order to cause the semiconductor device to operate normally-off. For example, an auxiliary electrode on third nitride semiconductor layer 14 may also be applied to a semiconductor device in which conductive nitride semiconductor layer 15 and part of gate electrode 24 are provided not on third nitride semiconductor layer 14 but on first nitride semiconductor layer 12 in which two-dimensional electron gas between third nitride semiconductor layer 14 and source electrode 21 is disrupted. It is also clear that in the second, third, and fourth modifications, a fourth nitride semiconductor layer 16 may be provided between auxiliary electrode 25 and third nitride semiconductor layer 14, as in the first modification. It is also clear that in the first to fourth modifications, the planar configuration of each electrode can be made similar to that shown in Fig. 3. In this case, in the second, third, and fourth modifications, the shapes of field plate electrodes 26, 28 and the portions of auxiliary electrode 27 that correspond to the field plate electrodes can be set appropriately depending on the shape of the auxiliary electrode. [Explanation of symbols]

[0033] 1, 2, 3, 4, 5, 9 Semiconductor device 11 Circuit Board 12 First nitride semiconductor layer 13 Second nitride semiconductor layer 14 Third nitride semiconductor layer 15 Conductive nitride semiconductor layer 16 Fourth nitride semiconductor layer 21 Source electrode (second main electrode) 22 drain electrode (first main electrode) 23 Insulating layer 24 Gate electrode (control electrode) 25, 27 Auxiliary electrode 26, 28 Field plate electrode

Claims

1. A semiconductor device in which a current flowing between a first main electrode and a second main electrode is controlled by a potential of a control electrode, a first nitride semiconductor layer; a second nitride semiconductor layer provided on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer; a third nitride semiconductor layer provided on a portion of an upper surface of the second nitride semiconductor layer and having a band gap narrower than the band gap of the second nitride semiconductor layer; Equipped with the first main electrode and the second main electrode are not in direct contact with the third nitride semiconductor layer and are formed on the first nitride semiconductor layer; the control electrode is formed on the third nitride semiconductor layer between the first main electrode and the second main electrode; a control electrode formed on the first main electrode and a second main electrode formed on the third nitride semiconductor layer;

2. A semiconductor device in which a current flowing between a first main electrode and a second main electrode is controlled by a potential of a control electrode, a first nitride semiconductor layer; a second nitride semiconductor layer provided on the first nitride semiconductor layer and having a band gap wider than that of the first nitride semiconductor layer; a third nitride semiconductor layer provided on a portion of an upper surface of the second nitride semiconductor layer and having a band gap narrower than the band gap of the second nitride semiconductor layer; Equipped with the first main electrode and the second main electrode are not in direct contact with the third nitride semiconductor layer and are formed on the first nitride semiconductor layer; the control electrode is formed on the third nitride semiconductor layer between the first main electrode and the second main electrode; a semiconductor device comprising: an auxiliary electrode locally formed on the third nitride semiconductor layer between the control electrode and the first main electrode, with a p-type fourth nitride semiconductor layer interposed therebetween.

3. 3. The semiconductor device according to claim 1, wherein the auxiliary electrode and the control electrode are connected to each other.

4. a potential applied to the first main electrode that is more positive than the second main electrode; 3. The semiconductor device according to claim 1, wherein, in the state where the current is turned off, a potential higher than a potential of the control electrode and lower than a potential of the first main electrode is applied to the auxiliary electrode.

5. 3. The semiconductor device according to claim 1, further comprising a field plate electrode on the second nitride semiconductor layer between the third nitride semiconductor layer and the first main electrode, with an insulating layer interposed therebetween.

6. 6. The semiconductor device according to claim 5, wherein the field plate electrode and the auxiliary electrode are connected to each other.

7. 3. The semiconductor device according to claim 1, wherein, in a plan view, the auxiliary electrodes are arranged in a dispersed manner in a second direction perpendicular to a first direction from the first main electrode toward the second main electrode.

Images