Nitride compound semiconductor devices

Abstract

The present invention provides a nitride-based compound semiconductor device that sufficiently reduces the electric field peak between the control electrode and the first main electrode on the high-potential side. [Solution] A nitride compound semiconductor device comprising: a first nitride compound semiconductor layer having a two-dimensional electron gas layer on top; a second nitride compound semiconductor layer having a larger band gap than the first layer; a first main electrode on the high-potential side and a second main electrode on the low-potential side electrically connected to the two-dimensional electron gas layer; a third nitride compound semiconductor layer having a smaller band gap than the second nitride compound semiconductor layer between the first and second main electrodes; a P-type semiconductor layer electrically connected to the second nitride compound semiconductor layer; and a control electrode thereon, wherein the third nitride compound semiconductor layer extends toward the first main electrode side than the P-type semiconductor layer; a first insulating film on the second nitride compound semiconductor layer between the third nitride compound semiconductor layer and the first main electrode; and a first auxiliary electrode thereon.

Description

Technical Field

[0001] The present disclosure relates to a nitride-based compound semiconductor device.

Background Art

[0002] When a hetero-junction is formed between a first nitride-based compound semiconductor layer (hereinafter also referred to as a nitride-based semiconductor layer or a nitride semiconductor layer) and a second nitride-based compound semiconductor layer having a composition different from that of the first nitride-based compound semiconductor layer, either or both of spontaneous polarization and piezo polarization occur, and a two-dimensional electron gas layer (2DEG layer) is generated in the first nitride-based compound semiconductor layer near the hetero-interface.

[0003] Furthermore, when a hetero-junction is formed between the second nitride-based compound semiconductor layer and a third nitride-based compound semiconductor layer having a composition different from that of the second nitride-based compound semiconductor layer on the second nitride-based compound semiconductor layer, either or both of spontaneous polarization and piezo polarization occur, and a two-dimensional hole gas layer (2DHG layer) is generated in the third nitride-based compound semiconductor layer near the hetero-interface.

[0004] When the third nitride-based compound semiconductor layer is formed so as to extend from under the gate electrode (hereinafter also referred to as a control electrode) to the drain electrode (hereinafter also referred to as the first main electrode on the high potential side), the portion where the third nitride-based compound semiconductor layer is extended becomes a polarization super-junction part (also referred to as a PSJ structure), and the electric field strength in that portion is made uniform.

[0005] Therefore, it is said that a nitride-based compound semiconductor device provided with a polarization super-junction part (hereinafter also referred to as a nitride-based semiconductor device or a nitride semiconductor device) can have high breakdown voltage characteristics.

[0006] A nitride-based compound semiconductor device equipped with a polarization superjunction (PSJ structure) is disclosed, for example, in Patent Document 1. In the nitride semiconductor device equipped with a polarization superjunction described in Patent Document 1, an electric field peak occurs at the drain electrode side end of the polarization superjunction. However, by providing a fourth nitride semiconductor layer with a floating potential between the polarization superjunction and the drain electrode, the electric field intensity peak can be dispersed, thereby reducing the electric field intensity peak. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-123161 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, even when a fourth nitride semiconductor layer with a floating potential was provided between the polarization superjunction and the drain electrode, an electric field peak was generated on the drain electrode side of the fourth nitride semiconductor layer, making it difficult to sufficiently reduce the electric field peak between the gate electrode and the drain electrode.

[0009] This disclosure has been made in view of the above-mentioned problems and aims to provide a nitride-based compound semiconductor device that sufficiently reduces the electric field peak between the gate electrode (control electrode) and the drain electrode (first main electrode on the high-potential side). [Means for solving the problem]

[0010] To achieve the above objective, the present disclosure provides a first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top of it; a second nitride-based compound semiconductor layer provided on the first nitride-based compound semiconductor layer and having a larger band gap than the first nitride-based compound semiconductor layer; a first main electrode on the high-potential side electrically connected to the two-dimensional electron gas layer; a second main electrode on the low-potential side electrically connected to the two-dimensional electron gas layer; and a second main electrode provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode, which has a larger band gap than the second nitride-based compound semiconductor layer. The present invention provides a nitride-based compound semiconductor device comprising: a third nitride-based compound semiconductor layer having a small band gap; a P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer; and a control electrode provided on the P-type semiconductor layer, wherein the third nitride-based compound semiconductor layer extends further toward the first main electrode than the P-type semiconductor layer; and further comprising a first insulating film provided on the second nitride-based compound semiconductor layer between the third nitride-based compound semiconductor layer and the first main electrode; and a first auxiliary electrode provided on the first insulating film.

[0011] In such a nitride-based compound semiconductor device, by first extending the third nitride-based compound semiconductor layer below the control electrode toward the first main electrode side beyond the P-type semiconductor layer, the third nitride-based compound semiconductor layer becomes a polarization superjunction, and the electric field strength on the surface of the second nitride-based compound semiconductor layer is made uniform. Furthermore, by having a first insulating film and a first auxiliary electrode on top of it between the third nitride-based compound semiconductor layer and the first main electrode, the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side that forms the polarization superjunction is mitigated. Therefore, the electric field can be borne more smoothly across the entire third nitride-based compound semiconductor layer, and the electric field peak between the control electrode and the first main electrode on the high-potential side can be sufficiently reduced.

[0012] Furthermore, it is preferable that the first auxiliary electrode is connected to the third nitride-based compound semiconductor layer.

[0013] As a result, the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side is further mitigated, thereby more reliably reducing the electric field peak between the control electrode and the first main electrode on the high-potential side.

[0014] Furthermore, it is preferable to have a fourth nitride-based compound semiconductor layer provided on the second nitride-based compound semiconductor layer between the first main electrode and the third nitride-based compound semiconductor layer, spaced apart from the first main electrode and the third nitride-based compound semiconductor layer.

[0015] This fourth nitride-based compound semiconductor layer forms a floating potential between the third nitride-based compound semiconductor layer that forms the polarization superjunction and the first main electrode. As a result, the peaks of the electric field strength are dispersed, and the electric field peak between the control electrode and the first main electrode on the high-potential side can be reduced more reliably.

[0016] Furthermore, it is preferable to have a second insulating film provided on the second nitride-based compound semiconductor layer between the fourth nitride-based compound semiconductor layer and the first main electrode, and a second auxiliary electrode provided on the second insulating film.

[0017] As a result, the electric field peak at the end of the fourth nitride-based compound semiconductor layer on the first main electrode side is mitigated, making it possible to more reliably reduce the electric field peak between the control electrode and the first main electrode on the high-potential side.

[0018] Furthermore, it is preferable that the second auxiliary electrode is connected to the fourth nitride-based compound semiconductor layer.

[0019] This further mitigates the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side, thereby more reliably reducing the electric field peak between the control electrode and the first main electrode on the high-potential side.

[0020] Further, the third nitride-based compound semiconductor layer is configured to be divided into a plurality between the control electrode and the first main electrode, and includes a plurality of P-type semiconductor layers on the plurality of third nitride-based compound semiconductor layers, and preferably has the control electrode or another control electrode electrically connected to the control electrode on the plurality of P-type semiconductor layers.

[0021] Thereby, by dividing the third nitride-based compound semiconductor layer, it is possible to suppress a decrease in the concentration of the two-dimensional electron gas layer where there is no third nitride-based compound semiconductor layer, and to reduce the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side.

[0022] Further, the third nitride-based compound semiconductor layer preferably has a plurality of protruding portions that continuously and / or intermittently extend in a direction from the control electrode to the first main electrode in a plan view.

[0023] Thereby, it is possible to suppress a decrease in the concentration of the two-dimensional electron gas layer where there is no protruding portion (i.e., where there is no third nitride-based compound semiconductor layer), and to reduce the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side.

[0024] Further, it preferably has a third auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode and electrically connected to the second main electrode.

[0025] As a result, due to the influence of the low potential of the third auxiliary electrode, the electric field peak at the end of the control electrode on the first main electrode side decreases, and accordingly, the electric field in the third nitride-based compound semiconductor layer that forms the polarization superjunction directly below and around the end of the third auxiliary electrode on the first main electrode side increases. As a result, the electric field borne by the entire third nitride-based compound semiconductor layer from directly below the third auxiliary electrode and its periphery to the end of the third nitride-based compound semiconductor layer on the first main electrode side increases. Thereby, the electric field at the end of the third nitride-based compound semiconductor layer on the first main electrode side can be reduced, and the electric field peak between the control electrode and the first main electrode on the high potential side can be more reliably reduced.

[0026] Further, the distance from the end of the control electrode on the first main electrode side to the end of the third auxiliary electrode on the first main electrode side is preferably not more than half of the distance that the third nitride-based compound semiconductor layer extends on the first main electrode side from the P-type semiconductor layer.

[0027] If the relationship between the third auxiliary electrode and the third nitride-based compound semiconductor layer is within the above range, due to the influence of the low potential of the third auxiliary electrode, the trough of the electric field strength between the electric field peak at the end of the control electrode on the first main electrode side and the electric field peak at the end of the third nitride-based compound semiconductor layer on the first main electrode side can be made shallower. Thereby, an increase in the electric field at the end of the third nitride-based compound semiconductor layer on the first main electrode side can be further reduced.

[0028] Furthermore, this disclosure includes a first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top of it, a second nitride-based compound semiconductor layer provided on the first nitride-based compound semiconductor layer and having a larger band gap than the first nitride-based compound semiconductor layer, a first main electrode on the high-potential side electrically connected to the two-dimensional electron gas layer, a second main electrode on the low-potential side electrically connected to the two-dimensional electron gas layer, and a second nitride-based compound semiconductor layer provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode. The present invention provides a nitride compound semiconductor device comprising: a third nitride compound semiconductor layer having a band gap smaller than that of the first main electrode; a P-type semiconductor layer electrically connected to the third nitride compound semiconductor layer; and a control electrode provided on the P-type semiconductor layer, wherein the third nitride compound semiconductor layer extends toward the first main electrode than the P-type semiconductor layer; and further comprises an auxiliary electrode provided above the third nitride compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode.

[0029] In such a nitride-based compound semiconductor device, by extending the third nitride-based compound semiconductor layer below the control electrode toward the first main electrode beyond the P-type semiconductor layer, the third nitride-based compound semiconductor layer becomes a polarization superjunction, and the electric field strength is made uniform. Furthermore, by providing an auxiliary electrode above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode, the electric field peak at the end of the control electrode toward the first main electrode is reduced due to the influence of the low potential of this auxiliary electrode. As a result, the electric field in the third nitride-based compound semiconductor layer forming the polarization superjunction, directly below and around the end of the auxiliary electrode toward the first main electrode, increases. Consequently, the electric field borne by the entire third nitride-based compound semiconductor layer from directly below and around the auxiliary electrode toward the end of the third nitride-based compound semiconductor layer toward the first main electrode increases. This reduces the electric field at the end of the third nitride-based compound semiconductor layer toward the first main electrode, and reduces the electric field peak between the control electrode and the first main electrode on the high-potential side. [Effects of the Invention]

[0030] As described above, with the nitride-based compound semiconductor device of this disclosure, the electric field peak near the first main electrode side edge of the third nitride-based compound semiconductor layer that forms the polarization superjunction is mitigated.

[0031] Furthermore, by providing an auxiliary electrode above the third nitride-based compound semiconductor layer and electrically connected to the second main electrode, the auxiliary electrode electrically connected to the second main electrode on the low-potential side becomes low-potential. Influenced by the low potential of this auxiliary electrode, the electric field peak at the end of the control electrode on the first main electrode side decreases, and the electric field in the third nitride-based compound semiconductor layer forming the polarization superjunction directly below the end of the auxiliary electrode on the first main electrode side increases. As a result, the electric field near the end of the third nitride-based compound semiconductor layer on the first main electrode side can be reduced, and the electric field peak between the control electrode and the first main electrode on the high-potential side can be reduced. [Brief explanation of the drawing]

[0032] [Figure 1] This is a cross-sectional view showing a first embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 2] This is a cross-sectional view showing a second embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 3] This is a cross-sectional view showing a third embodiment of a nitride-based compound semiconductor device according to the present disclosure. [Figure 4] This is a top view showing a fourth embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 5] This is a cross-sectional view showing a fourth embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 6] This is a cross-sectional view showing an application example of a fourth embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 7] This is a cross-sectional view showing a fifth embodiment of a nitride-based compound semiconductor device of the present disclosure. [Figure 8] This is a cross-sectional view showing a sixth embodiment of a nitride-based compound semiconductor device according to the present disclosure. [Figure 9]This graph shows the simulation results of the electric field strength when the distance W is changed as a parameter in the sixth embodiment. [Figure 10] This is a cross-sectional view showing an example of the configuration of the first auxiliary electrode and insulating layer. [Figure 11] This is a cross-sectional view showing an example of the configuration of the third auxiliary electrode. [Modes for carrying out the invention]

[0033] As described above, there was a need for a nitride-based compound semiconductor device that could sufficiently reduce the electric field peak between the gate electrode (control electrode) and the drain electrode (the first main electrode on the high-potential side).

[0034] Therefore, the inventors conducted diligent studies and found that by forming a polarization superjunction (PSJ structure) with a nitride-based compound semiconductor layer extended toward the first main electrode side from the P-type semiconductor layer, and by having an insulating film between this nitride-based compound semiconductor layer and the first main electrode, and an auxiliary electrode on the insulating film, the electric field peak between the gate electrode (control electrode) and the drain electrode (the first main electrode on the high potential side) can be sufficiently reduced, thus completing this disclosure.

[0035] That is, the present disclosure provides a first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top of it, a second nitride-based compound semiconductor layer provided on the first nitride-based compound semiconductor layer and having a larger band gap than the first nitride-based compound semiconductor layer, a first main electrode on the high potential side electrically connected to the two-dimensional electron gas layer, a second main electrode on the low potential side electrically connected to the two-dimensional electron gas layer, and a second main electrode provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode and having a smaller band gap than the second nitride-based compound semiconductor layer A nitride-based compound semiconductor device is characterized by comprising: a third nitride-based compound semiconductor layer having a gap; a P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer; and a control electrode provided on the P-type semiconductor layer, wherein the third nitride-based compound semiconductor layer extends further toward the first main electrode than the P-type semiconductor layer; and further comprising a first insulating film provided on the second nitride-based compound semiconductor layer between the third nitride-based compound semiconductor layer and the first main electrode; and a first auxiliary electrode provided on the first insulating film.

[0036] Furthermore, this disclosure includes a first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top of it, a second nitride-based compound semiconductor layer provided on the first nitride-based compound semiconductor layer and having a larger band gap than the first nitride-based compound semiconductor layer, a first main electrode on the high-potential side electrically connected to the two-dimensional electron gas layer, a second main electrode on the low-potential side electrically connected to the two-dimensional electron gas layer, and a second nitride-based compound semiconductor layer provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode. A nitride-based compound semiconductor device is characterized by comprising: a third nitride-based compound semiconductor layer having a band gap smaller than that of the layer; a P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer; and a control electrode provided on the P-type semiconductor layer, wherein the third nitride-based compound semiconductor layer extends toward the first main electrode side than the P-type semiconductor layer; and further comprising an auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode.

[0037] The following is a detailed description of this disclosure with reference to the drawings, but the disclosure is not limited thereto.

[0038] <First Embodiment>

[0039] Figure 1 is a cross-sectional view showing a first embodiment of the nitride compound semiconductor device of the present disclosure.

[0040] First, the nitride-based compound semiconductor device of this embodiment includes a first nitride-based compound semiconductor layer 12 having a two-dimensional electron gas layer (not shown) formed on top of it, a second nitride-based compound semiconductor layer 13 provided on the first nitride-based compound semiconductor layer 12 and having a larger band gap than the first nitride-based compound semiconductor layer 12, a first main electrode 22 on the high-potential side electrically connected to the two-dimensional electron gas layer (not shown), a second main electrode 21 on the low-potential side electrically connected to the two-dimensional electron gas layer (not shown), and a second nitride-based compound semiconductor layer 13 provided between the first main electrode 22 and the second main electrode 21. The semiconductor device comprises a third nitride-based compound semiconductor layer 14 having a smaller band gap than the second nitride-based compound semiconductor layer 13, a P-type semiconductor layer 15 electrically connected to the third nitride-based compound semiconductor layer 14, and a control electrode 24 provided on the P-type semiconductor layer 15. The third nitride-based compound semiconductor layer 14 extends further toward the first main electrode 22 than the P-type semiconductor layer 15. Furthermore, it includes a first insulating film 23b provided on the second nitride-based compound semiconductor layer 13 between the third nitride-based compound semiconductor layer 14 and the first main electrode 22, and a first auxiliary electrode 27 provided on the first insulating film 23b.

[0041] In such a nitride-based compound semiconductor device, first, by extending the third nitride-based compound semiconductor layer 14, which is electrically connected to the P-type semiconductor layer 15, toward the first main electrode 22 side beyond the P-type semiconductor layer 15, the portion of the third nitride-based compound semiconductor layer 14 that extends toward the first main electrode 22 side beyond the P-type semiconductor layer 15 becomes a polarization superjunction, and the electric field strength is made uniform. Furthermore, by having a first insulating film 23b and a first auxiliary electrode 27 on top of it between the third nitride-based compound semiconductor layer 14 and the first main electrode 22, the electric field peak at the end of the third nitride-based compound semiconductor layer 14 toward the first main electrode 22 that forms the polarization superjunction is mitigated. Therefore, the electric field can be borne more smoothly across the entire third nitride-based compound semiconductor layer 14, and the electric field peak between the control electrode 24 and the first main electrode 22 on the high-potential side can be sufficiently reduced.

[0042] Furthermore, although not particularly limited, it is preferable that the first auxiliary electrode 27 is connected to the third nitride-based compound semiconductor layer 14.

[0043] This makes it easier to eliminate non-uniformity of the electric field and more reliably reduces the electric field peak between the control electrode 24 and the first main electrode 22 on the high-potential side.

[0044] This embodiment will be described in more detail below.

[0045] A first nitride-based compound semiconductor layer 12, made of, for example, undoped GaN, is provided on a substrate 11 formed of silicon, silicon carbide, or sapphire, and this first nitride-based compound semiconductor layer 12 can be a channel layer.

[0046] Although not particularly limited, a buffer layer such as AlN or AlGaN may be provided between the substrate 11 and the first nitride-based compound semiconductor layer (channel layer) 12.

[0047] A barrier layer can be formed by providing a second nitride-based compound semiconductor layer 13, which is not particularly limited but is made of, for example, AlGaN, on the first nitride-based compound semiconductor layer (channel layer) 12.

[0048] A barrier layer 13 of a second nitride-based compound semiconductor layer, made of, for example, AlGaN (but not limited to), which has a larger band gap energy than the first nitride-based compound semiconductor layer (channel layer) 12, is provided on the first nitride-based compound semiconductor layer (channel layer) 12. As a result, a two-dimensional electron gas layer (not shown) is formed on the first nitride-based compound semiconductor layer (channel layer) 12 side near the interface between the first nitride-based compound semiconductor layer (channel layer) 12 and the second nitride-based compound semiconductor layer (barrier layer) 13.

[0049] The second main electrode (source electrode) 21 on the low-potential side and the first main electrode (drain electrode) 22 on the high-potential side are preferably formed on a first nitride-based compound semiconductor layer (channel layer) 12 or a second nitride-based compound semiconductor layer (barrier layer) 13, although this is not particularly limited, and are electrically connected to the two-dimensional electron gas layer with low resistance.

[0050] Furthermore, a polarization superjunction (PSJ) is formed on a second nitride-based compound semiconductor layer (barrier layer) 13, which is separated from the first main electrode (drain electrode) 22 on the high-potential side. This third nitride-based compound semiconductor layer 14 is made of, for example, undoped GaN, which has a smaller bandgap energy than the second nitride-based compound semiconductor layer (barrier layer) 13. Within this third nitride-based compound semiconductor layer (PSJ) 14, a two-dimensional hole gas layer (not shown) is formed.

[0051] Furthermore, a control electrode (gate electrode) 24 is provided on the third nitride-based compound semiconductor layer (PSJ) 14 via a P-type semiconductor layer 15, which is not particularly limited but is made of, for example, P-type GaN or NiO. Note that the P-type semiconductor layer 15 and the control electrode (gate electrode) 24 only need to be electrically connected to the third nitride-based compound semiconductor layer (PSJ) 14, and may be provided on the first nitride-based compound semiconductor layer (channel layer) 12 between the third nitride-based compound semiconductor layer (PSJ) 14 and the second main electrode (source electrode) 21, rather than on the third nitride-based compound semiconductor layer (PSJ) 14.

[0052] Furthermore, in Figure 1, a first insulating film 23b is provided on the second nitride-based compound semiconductor layer (barrier layer) 13 between the third nitride-based compound semiconductor layer (PSJ) 14 and the first main electrode (drain electrode) 22 on the high-potential side, and a first auxiliary electrode 27 is provided on the insulating film 23b. The first auxiliary electrode 27 is not particularly limited, but may be in contact with the upper part of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side, or it may be separated from the third nitride-based compound semiconductor layer (PSJ) 14 to the extent that it is capacitively coupled with the third nitride-based compound semiconductor layer (PSJ) 14.

[0053] Although not particularly limited, the first auxiliary electrode 27 and the first main electrode (drain electrode) 22 on the high-potential side are separated.

[0054] Furthermore, although not particularly limited, the first auxiliary electrode 27 is formed of a conductive semiconductor such as conductive polysilicon or a conductor such as a metal, and at least a portion of the first auxiliary electrode 27 on the high-potential side toward the first main electrode (drain electrode) 22 is formed on a first insulating film 23b that is thicker than the third nitride-based compound semiconductor layer (PSJ) 14, and the lower surface of the first auxiliary electrode 27 is higher than the third nitride-based compound semiconductor layer (PSJ) 14 toward the first main electrode (drain electrode) 22 (away from the third nitride-based compound semiconductor layer (PSJ) 14).

[0055] The first insulating film 23b is provided on the second nitride-based compound semiconductor layer (barrier layer) 13. Furthermore, although not particularly limited, another insulating film 23a may be provided on the second nitride-based compound semiconductor layer (barrier layer) 13 between the second main electrode (source electrode) 21 and the control electrode (gate electrode) 24 on the low-potential side.

[0056] The first auxiliary electrode 27 in this embodiment is sometimes referred to as a field plate.

[0057] <Second Embodiment>

[0058] Figure 2 is a cross-sectional view showing a second embodiment of the nitride compound semiconductor device of the present disclosure.

[0059] While not particularly limited, the nitride-based compound semiconductor device of this embodiment preferably has a fourth nitride-based compound semiconductor layer 16 provided on a second nitride-based compound semiconductor layer 13 between the first main electrode 22 and the third nitride-based compound semiconductor layer 14, as shown in Figure 2, and spaced apart from the first main electrode 22 and the third nitride-based compound semiconductor layer 14.

[0060] This fourth nitride-based compound semiconductor layer 16 forms a floating potential between the third nitride-based compound semiconductor layer 14, which forms the polarization superjunction, and the first main electrode 22. As a result, the peak of the electric field strength on the first main electrode 22 side of the third nitride-based compound semiconductor layer (PSJ) 14 is dispersed and reduced, and the electric field peak between the control electrode 24 and the first main electrode 22 can be further reduced.

[0061] Furthermore, although not particularly limited, it is preferable to have a second insulating film 23c provided on the second nitride-based compound semiconductor layer 13 between the fourth nitride-based compound semiconductor layer 16 and the first main electrode 22, and a second auxiliary electrode 28 provided on the second insulating film 23c.

[0062] This reduces the electric field peak at the end of the fourth nitride-based compound semiconductor layer 16 on the side of the first main electrode 22.

[0063] Furthermore, although not particularly limited, it is preferable that the second auxiliary electrode 28 is connected to the fourth nitride-based compound semiconductor layer 16.

[0064] This reduces the electric field peak near the end of the fourth nitride-based compound semiconductor layer 16 on the first main electrode 22 side.

[0065] This embodiment will be described in more detail below.

[0066] Figure 2 of this embodiment is characterized in that, compared to Figure 1 of the first embodiment, a separated fourth nitride-based compound semiconductor layer 16 and a second auxiliary electrode 28 are provided between the third nitride-based compound semiconductor layer (PSJ) 14 and the first auxiliary electrode 27 and the first main electrode (drain electrode) 22.

[0067] It should be noted that this embodiment is not limited to the configuration shown in Figure 2. In Figure 2, a separated fourth nitride-based compound semiconductor layer 16 and a second auxiliary electrode 28 are provided between the third nitride-based compound semiconductor layer (PSJ) 14 and the first auxiliary electrode 27 and the first main electrode (drain electrode) 22. However, the embodiment is not limited to this configuration, and a configuration in which multiple fourth nitride-based compound semiconductor layers 16 and second auxiliary electrodes 28 are provided spaced apart from each other is also possible.

[0068] Furthermore, although not particularly limited, the fourth nitride-based compound semiconductor layer 16 may be formed from the same material as the third nitride-based compound semiconductor layer (PSJ) 14 (for example, undoped GaN). If the same material is used, it is possible to form them simultaneously, which is preferable.

[0069] Furthermore, although not particularly limited, the fourth nitride-based compound semiconductor layer 16 is shorter in dimensions than the third nitride-based compound semiconductor layer (PSJ) 14 in the direction in which the third nitride-based compound semiconductor layer (PSJ) 14 is stretched.

[0070] Furthermore, although not particularly limited, the fourth nitride-based compound semiconductor layer 16 is separated from the third nitride-based compound semiconductor layer (PSJ) 14 and the first main electrode (drain electrode) 22 on the high-potential side.

[0071] Furthermore, although not particularly limited, the second auxiliary electrode 28 may be formed from the same material as the first auxiliary electrode 27 (for example, a conductive semiconductor such as conductive polysilicon or a conductor such as a metal).

[0072] Furthermore, although not particularly limited, the second auxiliary electrode 28, like the first auxiliary electrode 27, is formed on a second insulating layer 23c that is thicker than the fourth nitride-based compound semiconductor layer 16, at least a portion of which is on the high-potential side of the first main electrode (drain electrode) 22, and the lower surface of the second auxiliary electrode 28 is higher than the fourth nitride-based compound semiconductor layer 16 on the first main electrode (drain electrode) 22 side (away from the fourth nitride-based compound semiconductor layer 16).

[0073] Furthermore, Patent Document 1 also discloses an example in which a separated fourth nitride-based compound semiconductor layer is provided between the third nitride-based compound semiconductor layer (PSJ) and the drain electrode. However, Patent Document 1 does not contain any description of the first auxiliary electrode 27, the second auxiliary electrode 28 (and the first insulating film 23b, the second insulating film 23c), etc., as in the above embodiment, and as a result, an electric field peak is generated near the drain electrode side edge of the fourth nitride-based compound semiconductor layer.

[0074] In contrast, in this embodiment, by providing a second insulating film 23c and a second auxiliary electrode 28, the electric field peak near the edge of the fourth nitride-based compound semiconductor layer 16 can be mitigated, and the electric field peak between the control electrode (gate electrode) 24 and the first main electrode (drain electrode) 22 can be sufficiently reduced.

[0075] In this embodiment, an example is shown in which both the first auxiliary electrode 27 (and the first insulating film 23b) and the second auxiliary electrode 28 (and the second insulating film 23c) are provided. However, the embodiment is not limited to this, and it is possible to omit either the first auxiliary electrode 27 (and the first insulating film 23b) or the second auxiliary electrode 28 (and the second insulating film 23c). For example, the second auxiliary electrode 28 (and the second insulating film 23c) may be omitted, and only the first auxiliary electrode 27 (and the first insulating film 23b) may be provided. Providing only one of the first auxiliary electrode 27 (and the first insulating film 23b) or the second auxiliary electrode 28 (and the second insulating film 23c) has the effect of reducing the electric field peak between the control electrode (gate electrode) 24 and the first main electrode (drain electrode) 22 on the high potential side. Of course, it goes without saying that providing both will have an even greater effect in reducing the electric field peak between the control electrode (gate electrode) 24 and the first main electrode (drain electrode) 22 on the high potential side.

[0076] Furthermore, Figure 2 shows a case where there are two fourth nitride-based compound semiconductor layers 16 and auxiliary electrodes, such as the first auxiliary electrode 27 and the second auxiliary electrode 28, which are provided between the control electrode (gate electrode) 24 and the first main electrode (drain electrode) 22 on the high-potential side. However, the number of fourth nitride-based compound semiconductor layers 16 and auxiliary electrodes is not limited to two. For example, one or more additional fourth nitride-based compound semiconductor layers 16, second auxiliary electrodes 28 (and second insulating film 23c) shown in Figure 2 may be provided.

[0077] The first auxiliary electrode 27 and the second auxiliary electrode 28 in this embodiment are sometimes referred to as field plates.

[0078] <Third Embodiment>

[0079] Figure 3 is a cross-sectional view showing a third embodiment of the nitride compound semiconductor device of the present disclosure.

[0080] While not particularly limited, the nitride compound semiconductor device of this embodiment preferably has, as shown in Figure 3, a third nitride compound semiconductor layer between the control electrode (gate electrode) 24 and the first main electrode (drain electrode) 22, divided into a plurality of third nitride compound semiconductor layers 14, 14', and each of the third nitride compound semiconductor layers 14, 14' has a P-type semiconductor layer 15, 15', a control electrode (gate electrode) 24 and a control electrode (gate electrode) 24' electrically connected to the control electrode (gate electrode) 24. Here, L0 in Figure 1 and L' in Figure 3 are approximately equal.

[0081] Since the third nitride-based compound semiconductor layer 14' has a P-type semiconductor layer 15' and a control electrode (gate electrode) 24' electrically connected to the control electrode (gate electrode) 24, the range of the third nitride-based compound semiconductor layer (PSJ) 14 that extends further toward the first main electrode 22 than the P-type semiconductor layer 15 is extended to the range indicated by L', and the electric field borne in the range L' is higher than that of the third nitride-based compound semiconductor layer (PSJ) 14 in Figure 1 where the range L0 is L1+L2. Therefore, the electric field peak generated on the drain electrode side of the fourth nitride semiconductor layer is reduced. Furthermore, compared to Figure 1, in Figure 3 the third nitride-based compound semiconductor layer (PSJ) 14 of Figure 1 is divided into multiple spaced-apart parts, becoming the third nitride-based compound semiconductor layer (PSJ) 14 and 14', with the first insulating film 23b formed between them.

[0082] Furthermore, a first auxiliary electrode 27 and a second auxiliary electrode 28, acting as field plates, are provided at the ends of the third nitride-based compound semiconductor layers (PSJ) 14 and 14' on the side of the first main electrode (drain electrode) 22. The field plate 27 may be electrically connected to the third nitride-based compound semiconductor layer (PSJ) 14, or it may be capacitively coupled to the third nitride-based compound semiconductor layer (PSJ) 14 at a distance from each other. The field plate 28 may be electrically connected to the third nitride-based compound semiconductor layer (PSJ) 14', or it may be capacitively coupled to the third nitride-based compound semiconductor layer (PSJ) 14' at a distance from each other.

[0083] Generally, when a third nitride-based compound semiconductor layer (PSJ) is provided, the concentration of the two-dimensional electron gas layer in the region directly beneath it decreases. However, in the L' region of this embodiment, since the third nitride-based compound semiconductor layer (PSJ) is not provided in the region where the first insulating film 23b is provided between the third nitride-based compound semiconductor layers (PSJ) 14, 14', the decrease in the concentration of the two-dimensional electron gas layer can be suppressed.

[0084] Furthermore, since the third nitride-based compound semiconductor layers (PSJs) 14 and 14' are located in the L' region, it is possible to obtain almost the same effect as when the PSL structure is located in the L0 region of Figure 1, thereby reducing the electric field peak at the drain electrode 22 side end of the third nitride-based compound semiconductor layers (PSJs) 14 and 14' closest to the drain electrode 22.

[0085] Furthermore, the electric field rises near the edge of the third nitride-based compound semiconductor layer (PSJ) 14 due to electric field concentration, and the electric field decreases considerably (valley) in the region between the third nitride-based compound semiconductor layer (PSJ) 14 on the drain electrode side and the third nitride-based compound semiconductor layer (PSJ) 14'. However, by providing the field plate 27, the electric field in this region can be raised. Therefore, the nitride-based compound semiconductor device in this embodiment can sufficiently reduce the electric field peak between the gate electrode (control electrode) and the drain electrode (first main electrode on the high potential side) while further suppressing the increase in on-resistance.

[0086] Furthermore, at least one of the multiple third nitride-based compound semiconductor layers 14' shown in Figure 3 may not have a P-type semiconductor layer 15' and a control electrode (gate electrode) 24' provided on the third nitride-based compound semiconductor layer 14, as in the embodiment shown in Figure 2.

[0087] <Fourth Embodiment>

[0088] Figures 4 to 6 show a fourth embodiment of the nitride-based compound semiconductor device of the present disclosure, where Figure 4 is a top view, Figure 5 is a cross-sectional view of Figure 4, and Figure 6 is a simplified top view showing an application example. In the figures, X, Y, and Z indicate directions.

[0089] While not particularly limited, the nitride-based compound semiconductor device of this embodiment, as shown in Figure 4, differs from Figure 1 in that the third nitride-based compound semiconductor layer 14 preferably has a plurality of protrusions 33 that extend continuously and / or intermittently in the direction from the control electrode (gate electrode) 24 to the first main electrode in a plan view. As shown in Figure 4, the control electrode (gate electrode) 24 side of the third nitride-based compound semiconductor layer 14 is connected, but a plurality of protrusions 33 are provided that extend continuously in the direction of the first main electrode (drain electrode) 22 of the third nitride-based compound semiconductor layer 14. In this way, the third nitride-based compound semiconductor layer 14 may extend in the X direction at multiple locations in the Y direction in a comb-like manner toward the first main electrode (drain electrode) 22.

[0090] Furthermore, a first insulating film 23c (not shown in Figure 4 to avoid obscuration, but shown in Figure 5) is provided on the second nitride-based compound semiconductor layer 13, where the protrusion 33 of the third nitride-based compound semiconductor layer 14 is not provided, and a field plate 27a is provided on top of it. The field plate 27a may be connected to the third nitride-based compound semiconductor layer 14, or it may be separated and capacitively coupled.

[0091] Generally, when a third nitride-based compound semiconductor layer (PSJ) is provided, the concentration of the two-dimensional electron gas layer in the region directly beneath it decreases. However, in this embodiment, there are no protrusions 33 in the region where the first insulating film 23c is provided, meaning that a third nitride-based compound semiconductor layer (PSJ) is not provided, so the decrease in the concentration of the two-dimensional electron gas layer can be suppressed.

[0092] Furthermore, since the protrusion 33 of the third nitride-based compound semiconductor layer (PSJ) 14 is located in the same region as L0 in Figure 1 in the X direction, the same effect as when the PSL structure is located in the L0 region of Figure 1 can be obtained, and the electric field peak at the drain electrode 22 side end of the third nitride-based compound semiconductor layer (PSJ) 14 closest to the drain electrode 22 can be reduced.

[0093] Furthermore, in the region of the third nitride-based compound semiconductor layer (PSJ) 14 where the protrusions 33 are not provided, the electric field decreases (below), but by providing the field plate 27, the electric field in this region can be raised. Therefore, the electric field borne directly below the field plate 27 increases, and the electric field peak between the gate electrode (control electrode) and the drain electrode (first main electrode on the high-potential side) can be sufficiently reduced. From the above, the nitride-based compound semiconductor device in this embodiment can sufficiently reduce the electric field peak between the gate electrode (control electrode) and the drain electrode (first main electrode on the high-potential side) while further suppressing the increase in on-resistance.

[0094] Furthermore, the protruding portion 33 is not limited to the configurations shown in Figures 4 and 5, and various other applications are conceivable. Some examples of applications are shown in Figure 6.

[0095] First, Figure 6(a) shows a configuration similar to that of Figures 4 and 5, in which the third nitride-based compound semiconductor layer 14 has a plurality of protrusions 33 that extend continuously in the direction from the control electrode to the first main electrode when viewed from above. Next, Figure 6(b) differs from Figures 4 and 5 in that, in addition to the plurality of protrusions 33a that extend continuously in the direction from the control electrode to the first main electrode when viewed from above, the third nitride-based compound semiconductor layer 14 has a plurality of intermittently extending protrusions 33b, and the protrusions 33b are configured in a so-called island-like manner.

[0096] In Figure 6(b), the island-shaped protrusion 33b is shown as being located at the top in the Y direction, but it is not limited to this; it may be located at the second or third position or later in the Y direction, or even at all positions. Also, in Figure 6(b), the configuration includes both a plurality of continuously extending protrusions 33a and a plurality of intermittently extending protrusions 33b, but it is not limited to this; it may consist only of intermittently extending protrusions 33b, or, as already shown in Figures 4, 5, and 6(a), it may consist only of a plurality of continuously extending protrusions 33a. Furthermore, as shown in Figure 3, the island-shaped protrusion 33b may have a P-type semiconductor layer 15' and a control electrode (gate electrode) 24' electrically connected to the control electrode (gate electrode) 24 on the island-shaped protrusion 33b composed of the third nitride-based compound semiconductor layer 14'. Furthermore, the island-shaped protrusions 33b may extend beyond the P-type semiconductor layer 15' to the first main electrode (drain electrode) 22.

[0097] <Fifth Embodiment>

[0098] Figure 7 is a cross-sectional view showing a fifth embodiment of the nitride compound semiconductor device of the present disclosure.

[0099] While not particularly limited, the nitride-based compound semiconductor device of this embodiment preferably has a third auxiliary electrode 29 provided above the third nitride-based compound semiconductor layer 14 between the first main electrode 22 and the control electrode 24, as shown in Figure 7, and electrically connected to the second main electrode 21.

[0100] As a result, the third auxiliary electrode 29, which is electrically connected to the second main electrode 21 on the low-potential side, becomes low-potential. Influenced by the potential of this third auxiliary electrode 29, the electric field peak near the end of the control electrode 24 on the first main electrode 22 side decreases, and consequently, the electric field in the third nitride-based compound semiconductor layer 14 that forms the polarization superjunction, directly below the end of the third auxiliary electrode 29 on the first main electrode 22 side, increases. Consequently, the electric field borne by the entire third nitride-based compound semiconductor layer 14 from directly below the third auxiliary electrode 29 to the end of the third nitride-based compound semiconductor layer 14 on the first main electrode 22 side increases. This reduces the electric field peak near the end of the third nitride-based compound semiconductor layer 14 on the first main electrode 22 side, and further reduces the electric field peak between the control electrode 24 and the first main electrode 22.

[0101] In realizing the configuration shown in Figure 7, although not limited thereto, it is conceivable to connect the second main electrode (source electrode) 21 on the low-potential side and the third auxiliary electrode 29 through a connection portion 30 in a VIA (through-hole) provided in the protective film on the third nitride-based compound semiconductor layer 14.

[0102] Furthermore, although not particularly limited, it is preferable that the distance from the end of the control electrode 24 on the first main electrode 22 side to the end of the third auxiliary electrode 29 on the first main electrode 22 side (distance W in Figure 7) is half or less of the distance that the third nitride-based compound semiconductor layer 14 extends toward the first main electrode 22 side than the P-type semiconductor layer 15 (distance L in Figure 7).

[0103] If the relationship between the third auxiliary electrode 29 and the third nitride-based compound semiconductor layer 14 is within the above range, the electric field of the third nitride-based compound semiconductor layer 14 beneath the third auxiliary electrode 29 will increase due to the influence of the low potential of the third auxiliary electrode 29. This will make the electric field borne by the entire third nitride-based compound semiconductor layer 14 forming the polarization superjunction more uniform, reduce the electric field peak at the end of the third nitride-based compound semiconductor layer 14 on the first main electrode 22 side, and more reliably reduce the electric field peak between the control electrode 24 and the first main electrode 22 on the high potential side.

[0104] In this embodiment, the bottom surface of the third auxiliary electrode 29 may be positioned higher than the bottom surface of the first auxiliary electrode 27. Furthermore, the first auxiliary electrode 27 and the third auxiliary electrode 29 in this embodiment are sometimes referred to as field plates.

[0105] <Sixth Embodiment> As shown in Figure 8, the nitride-based compound semiconductor device of this embodiment comprises a first nitride-based compound semiconductor layer 12 having a two-dimensional electron gas layer (not shown) formed on top of it, a second nitride-based compound semiconductor layer 13 provided on the first nitride-based compound semiconductor layer 12 and having a larger band gap than the first nitride-based compound semiconductor layer 12, a first main electrode 22 on the high-potential side electrically connected to the two-dimensional electron gas layer (not shown), a second main electrode 21 on the low-potential side electrically connected to the two-dimensional electron gas layer (not shown), and a second nitride-based compound between the first main electrode 22 and the second main electrode 21. The device includes a third nitride-based compound semiconductor layer 14 provided on a monocrystalline semiconductor layer 13 and having a smaller band gap than the second nitride-based compound semiconductor layer 13, a P-type semiconductor layer 15 electrically connected to the third nitride-based compound semiconductor layer 14, and a control electrode 24 provided on the P-type semiconductor layer 15, wherein the third nitride-based compound semiconductor layer 14 extends further toward the first main electrode 22 than the P-type semiconductor layer 15, and further includes an auxiliary electrode 29A provided above the third nitride-based compound semiconductor layer 14 between the first main electrode 22 and the control electrode 24 and electrically connected to the second main electrode 21.

[0106] In such a nitride-based compound semiconductor device, first, by extending the third nitride-based compound semiconductor layer 14 below the control electrode 24 toward the first main electrode 22 than the P-type semiconductor layer 15, the third nitride-based compound semiconductor layer 14 becomes a polarization superjunction, and the electric field strength is made uniform. Furthermore, by providing an auxiliary electrode 29A above the third nitride-based compound semiconductor layer 14 between the first main electrode 22 and the control electrode 24 and electrically connected to the second main electrode 21, the auxiliary electrode 29A, which is electrically connected to the second main electrode 21 on the low-potential side, becomes low-potential. Due to the influence of this low potential of the auxiliary electrode 29A, the electric field peak near the end of the control electrode 24 toward the first main electrode 22 decreases, and as a result, the electric field in the third nitride-based compound semiconductor layer 14 that forms the polarization superjunction directly below the end of the auxiliary electrode 29A toward the first main electrode 22 increases. As a result, the electric field borne by the entire third nitride-based compound semiconductor layer 14 increases from directly below the auxiliary electrode 29A to the end of the third nitride-based compound semiconductor layer 14 on the first main electrode 22 side. This reduces the electric field peak at the end of the third nitride-based compound semiconductor layer 14 on the first main electrode 22 side, and thus reduces the electric field peak between the control electrode 24 and the first main electrode 22.

[0107] This embodiment will be described in more detail below.

[0108] As described above, by providing the first auxiliary electrode described in the first to fifth embodiments, the electric field peak generated at the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the high-potential side of the first main electrode (drain electrode) 22 can be suppressed, and as a result, the electric field peak between the gate electrode (control electrode) and the drain electrode (the first main electrode on the high-potential side) can be reduced. Further investigation revealed that by providing an auxiliary electrode like that of the sixth embodiment instead of the first auxiliary electrode of the first to fifth embodiments, the electric field peak at the end of the control electrode (gate electrode) 24 on the first main electrode (drain electrode) 22 side can also be suppressed, and as a result, the electric field peak between the gate electrode (control electrode) and the drain electrode (the first main electrode on the high-potential side) can be reduced. In other words, this is equivalent to the structure in the fifth embodiment described above, without the first auxiliary electrode 27.

[0109] Therefore, in this embodiment, as shown in Figure 8, the auxiliary electrode 29A connected to the second main electrode (source electrode) 21 on the low-potential side is provided on the first main electrode (drain electrode) 22 side, rather than on the end of the control electrode (gate electrode) 24 on the first main electrode (drain electrode) 22 side.

[0110] In realizing the configuration shown in Figure 8, although not particularly limited, it is conceivable to connect the second main electrode (source electrode) 21 on the low-potential side and the auxiliary electrode 29A through a connection portion 30 in a VIA (through-hole) provided in the protective film on the third nitride-based compound semiconductor layer 14.

[0111] Influenced by the potential of the auxiliary electrode 29A, the electric field peak at the end of the control electrode (gate electrode) 24 on the first main electrode (drain electrode) 22 side decreases. As a result, the electric field in the third nitride-based compound semiconductor layer (PSJ) 14 directly below the end of the auxiliary electrode 29A on the first main electrode (drain electrode) 22 side increases, and the electric field borne by the entire third nitride-based compound semiconductor layer (PSJ) 14 from directly below the auxiliary electrode 29A to the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side increases. This makes it possible to reduce the electric field peak near the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side.

[0112] Here, the extension distance W of the auxiliary electrode 29A from the control electrode (gate electrode) 24 is not particularly limited, but it is desirable that it be less than half the distance L of the third nitride-based compound semiconductor layer (PSJ) 14 extending toward the first main electrode 22 than the P-type semiconductor layer 15, and more preferably less than one-third.

[0113] As described in the fifth embodiment, it is preferable that a sufficient difference (corresponding to "LW" in Figure 8) is secured between the end of the auxiliary electrode 29A on the first main electrode 22 side and the distance (distance L in Figure 8) to which the third nitride-based compound semiconductor layer 14 extends further toward the first main electrode 22 than the P-type semiconductor layer 15. The electric field borne in the third nitride-based compound semiconductor layer (PSJ) 14 directly beneath the second main electrode 21 increases under the influence of the auxiliary electrode 29A electrically connected to the second main electrode 21, and the electric field peak at the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side can be suppressed more stably. Therefore, although not particularly limited, the overhang distance W from the control electrode (gate electrode) 24 is preferably half or less of the length L to which the third nitride-based compound semiconductor layer (PSJ) 14 extends further toward the first main electrode 22 than the P-type semiconductor layer 15, and more preferably one-third or less.

[0114] Furthermore, although not particularly limited in this embodiment, it is even more preferable if a first auxiliary electrode 27 (and a first insulating film 23b) is provided at the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side, as this can further reduce electric field concentration at the end of the third nitride-based compound semiconductor layer (PSJ) 14 on the first main electrode (drain electrode) 22 side.

[0115] Figure 9 shows the simulation results of the electric field strength when the overhang distance W of the auxiliary electrode 29A is changed in the structure shown in Figure 8 of this embodiment.

[0116] In Figure 9, the horizontal axis represents the measurement position in the lateral direction within the third nitride-based compound semiconductor layer (PSJ) 14 in Figure 8, and the vertical axis represents the electric field strength. Particularly representative measurement positions are "G right end," which corresponds to the right end of the control electrode (gate electrode) 24 in Figure 8, and "PSJ right end," which corresponds to the right end of the third nitride-based compound semiconductor layer (PSJ) 14. From Figure 9, it can be seen that the electric field strength rises at "G right end" and peaks at "PSJ right end." Furthermore, the distance "L" between "G right end" and "PSJ right end" is precisely the distance L in Figure 8.

[0117] Curve A in Figure 9 shows the case where auxiliary electrode 29A is provided, and curve B shows the case where auxiliary electrode 29A is not provided. Looking at Figure 9, it can be seen that the electric field strength increases around position 15 where auxiliary electrode 29A is provided in curve A, and the electric field load increases throughout the entire area where the third nitride-based compound semiconductor layer (PSJ) 14 is provided.

[0118] Furthermore, compared to curve B, curve A shows a lower peak value of electric field strength at the "right end of the PSJ," indicating that the electric field peak between the control electrode 24 and the first main electrode 22 on the high-potential side can be reduced.

[0119] The auxiliary electrode 29A in this embodiment is sometimes referred to as a field plate. Furthermore, the auxiliary electrode 29A in this embodiment may also be adapted to the first to fourth embodiments.

[0120] (others) The following describes the common points of the first to fourth embodiments described above.

[0121] The first auxiliary electrodes 27, 27a and the second auxiliary electrode 28 are not connected to the third nitride-based compound semiconductor layer 14, 14', but may be electrically connected to the gate electrodes 24, 24' or the source electrode 21.

[0122] Figure 10 is a cross-sectional view showing an example configuration of the first auxiliary electrode 27 and the first insulating film 23b. Figure 10(a) shows the same configuration as shown in Figures 1-7, but Figure 10(b) shows the contact surface 31 of the first auxiliary electrode 27 and the first insulating film 23b angled. Although not particularly limited, by angling the contact surface 31, the bottom surface of the first auxiliary electrode 27 gradually moves away upward, thus making the change in the electric field more gradual.

[0123] The third auxiliary electrode 29 in the fifth embodiment and the auxiliary electrode 29A in the sixth embodiment may be provided such that the height of the bottom gradually increases toward the drain electrode 22 side. For example, steps may be formed so that they ascend in a staircase-like manner toward the drain electrode 22 side.

[0124] Figure 11 is a cross-sectional view showing an example configuration of the third auxiliary electrode 29, and the same applies to the auxiliary electrode 29A in the sixth embodiment. Figure 11(a) shows the same configuration as shown in Figures 7 and 8, but Figure 11(b) shows the bottom surface 32 of the third auxiliary electrode 29 tilted. Although not particularly limited, tilting the bottom surface 32 gradually increases the height of the bottom surface 32 of the third auxiliary electrode 29, thereby slowing down the change in the electric field.

[0125] Furthermore, Figure 11(c) shows a configuration in which the third auxiliary electrode 29 is composed of multiple third auxiliary electrodes 29a, 29b, and 29c, with the height of the bottom gradually increasing toward the drain electrode 22. Although not particularly limited, gradually increasing the height of the bottom causes the bottom surface of the third auxiliary electrode 29 to gradually move away upwards, thereby slowing down the change in the electric field.

[0126] In Figure 11(c), the third auxiliary electrode is composed of multiple third auxiliary electrodes 29a, 29b, and 29c, but this is not particularly limited. Alternatively, the bottom surface of one of the third auxiliary electrodes may be made stepped to create a step-like structure, for example, so that it ascends in a step-like manner toward the drain electrode 22. Also, in Figure 11(c), the multiple third auxiliary electrodes 29a, 29b, and 29c may all be provided above the third nitride-based compound semiconductor layer (PSJ) 14. However, when adapted to the structure of Figure 2, auxiliary electrode 29a may be provided above the third nitride-based compound semiconductor layer (PSJ) 14, auxiliary electrode 29b above the first insulating film 23b, and auxiliary electrode 29c above the fourth nitride-based compound semiconductor layer 16.

[0127] This disclosure includes the following aspects: [1]: A first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top, A second nitride-based compound semiconductor layer is provided on the first nitride-based compound semiconductor layer and has a larger band gap than the first nitride-based compound semiconductor layer, The first main electrode on the high-potential side is electrically connected to the two-dimensional electron gas layer, A second main electrode on the low-potential side, electrically connected to the two-dimensional electron gas layer, A third nitride-based compound semiconductor layer is provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode, and has a smaller band gap than the second nitride-based compound semiconductor layer. A P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer, The P-type semiconductor layer includes a control electrode, The third nitride-based compound semiconductor layer is extended toward the first main electrode side than the P-type semiconductor layer. Furthermore, a first insulating film is provided on the second nitride-based compound semiconductor layer between the third nitride-based compound semiconductor layer and the first main electrode, A nitride-based compound semiconductor device characterized by having a first auxiliary electrode provided on the first insulating film. [2]: The nitride-based compound semiconductor device according to [1] above, characterized in that the first auxiliary electrode is connected to the third nitride-based compound semiconductor layer. [3]: A nitride-based compound semiconductor device according to [1] or [2] above, characterized in that it has a fourth nitride-based compound semiconductor layer provided on the second nitride-based compound semiconductor layer between the first main electrode and the third nitride-based compound semiconductor layer, spaced apart from the first main electrode and the third nitride-based compound semiconductor layer. [4]: A second insulating film is provided on the second nitride-based compound semiconductor layer between the fourth nitride-based compound semiconductor layer and the first main electrode, The nitride compound semiconductor device according to [3] above, characterized by having a second auxiliary electrode provided on the second insulating film. [5]: The nitride-based compound semiconductor device according to [4] above, characterized in that the second auxiliary electrode is connected to the fourth nitride-based compound semiconductor layer. [6]: The nitride-based compound semiconductor device according to any one of [1] to [5] above, characterized in that the third nitride-based compound semiconductor layer is divided into multiple parts between the control electrode and the first main electrode, and comprises multiple P-type semiconductor layers on the multiple third nitride-based compound semiconductor layers, and has the control electrode or other control electrodes electrically connected to the control electrode on the multiple P-type semiconductor layers. [7]: The nitride-based compound semiconductor device according to any one of [1] to [6] above, characterized in that the third nitride-based compound semiconductor layer has a plurality of protrusions that extend continuously and / or intermittently in the direction from the control electrode to the first main electrode in a plan view. [8]: A nitride-based compound semiconductor device according to any one of [1] to [7] above, characterized in that it has a third auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode. [9]: The nitride-based compound semiconductor device according to [8] above, characterized in that the distance from the end of the control electrode on the first main electrode side to the end of the third auxiliary electrode on the first main electrode side is less than or equal to half the distance that the third nitride-based compound semiconductor layer extends toward the first main electrode side than the P-type semiconductor layer.

[10] : A first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top, A second nitride-based compound semiconductor layer is provided on the first nitride-based compound semiconductor layer and has a larger band gap than the first nitride-based compound semiconductor layer, The first main electrode on the high-potential side is electrically connected to the two-dimensional electron gas layer, A second main electrode on the low-potential side, electrically connected to the two-dimensional electron gas layer, A third nitride-based compound semiconductor layer is provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode, and has a smaller band gap than the second nitride-based compound semiconductor layer. A P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer, The P-type semiconductor layer includes a control electrode, The third nitride-based compound semiconductor layer is extended toward the first main electrode side than the P-type semiconductor layer. Furthermore, the nitride-based compound semiconductor device is characterized by having an auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode.

[0128] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Explanation of symbols]

[0129] 11...Substrate, 12...First nitride-based compound semiconductor layer (channel layer), 13…Second nitride-based compound semiconductor layer (barrier layer), 14, 14'... Third nitride-based compound semiconductor layer (PSJ), 15, 15'...P-type semiconductor layer, 16...Fourth nitride-based compound semiconductor layer, 21... The second main electrode (source electrode) on the low-potential side, 22...First main electrode (drain electrode) on the high-potential side, 23a...Other insulating film, 23b...First insulating film, 23c...Second insulating film, 24, 24'... control electrode (gate electrode), 27, 27a...First auxiliary electrode (field plate), 28...Second auxiliary electrode, 29, 29a, 29b, 29c... Third auxiliary electrode, 29A...Auxiliary electrode electrically connected to the second main electrode, 30...Connection part, 31...Contact surface, 32...Bottom surface, 33, 33a, 33b...Protruding part. A, B... curves, L, L0, L1, L2, L', W... distance, X, Y, Z... directions.

Claims

1. A first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top, A second nitride-based compound semiconductor layer is provided on the first nitride-based compound semiconductor layer and has a larger band gap than the first nitride-based compound semiconductor layer, The first main electrode on the high-potential side is electrically connected to the two-dimensional electron gas layer, A second main electrode on the low-potential side, electrically connected to the two-dimensional electron gas layer, A third nitride-based compound semiconductor layer is provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode, and has a smaller band gap than the second nitride-based compound semiconductor layer. A P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer, The P-type semiconductor layer includes a control electrode, The third nitride-based compound semiconductor layer is extended toward the first main electrode side than the P-type semiconductor layer. Furthermore, a first insulating film is provided on the second nitride-based compound semiconductor layer between the third nitride-based compound semiconductor layer and the first main electrode, A nitride-based compound semiconductor device characterized by having a first auxiliary electrode provided on the first insulating film.

2. The nitride-based compound semiconductor device according to claim 1, characterized in that the first auxiliary electrode is connected to the third nitride-based compound semiconductor layer.

3. The nitride-based compound semiconductor device according to claim 1, further comprising a fourth nitride-based compound semiconductor layer provided on the second nitride-based compound semiconductor layer between the first main electrode and the third nitride-based compound semiconductor layer, spaced apart from the first main electrode and the third nitride-based compound semiconductor layer.

4. A second insulating film is provided on the second nitride-based compound semiconductor layer between the fourth nitride-based compound semiconductor layer and the first main electrode, The nitride compound semiconductor device according to claim 3, characterized in that it has a second auxiliary electrode provided on the second insulating film.

5. The nitride-based compound semiconductor device according to claim 4, characterized in that the second auxiliary electrode is connected to the fourth nitride-based compound semiconductor layer.

6. The nitride-based compound semiconductor device according to claim 1 or 2, characterized in that the third nitride-based compound semiconductor layer is divided into multiple parts between the control electrode and the first main electrode, and the plurality of P-type semiconductor layers are provided on the plurality of third nitride-based compound semiconductor layers, and the plurality of P-type semiconductor layers have the control electrode or other control electrodes electrically connected to the control electrode.

7. The nitride-based compound semiconductor device according to claim 1 or 2, characterized in that the third nitride-based compound semiconductor layer has a plurality of protrusions that, in a plan view, extend continuously and / or intermittently from the control electrode in the direction of the first main electrode.

8. The nitride-based compound semiconductor device according to any one of claims 1 to 5, characterized in that it has a third auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode.

9. The nitride-based compound semiconductor device according to claim 8, characterized in that the distance from the end of the control electrode on the first main electrode side to the end of the third auxiliary electrode on the first main electrode side is less than or equal to half the distance that the third nitride-based compound semiconductor layer extends toward the first main electrode side than the P-type semiconductor layer.

10. A first nitride-based compound semiconductor layer having a two-dimensional electron gas layer formed on top, A second nitride-based compound semiconductor layer is provided on the first nitride-based compound semiconductor layer and has a larger band gap than the first nitride-based compound semiconductor layer, The first main electrode on the high-potential side is electrically connected to the two-dimensional electron gas layer, A second main electrode on the low-potential side, electrically connected to the two-dimensional electron gas layer, A third nitride-based compound semiconductor layer is provided on the second nitride-based compound semiconductor layer between the first main electrode and the second main electrode, and has a smaller band gap than the second nitride-based compound semiconductor layer. A P-type semiconductor layer electrically connected to the third nitride-based compound semiconductor layer, The P-type semiconductor layer includes a control electrode, The third nitride-based compound semiconductor layer is extended toward the first main electrode side than the P-type semiconductor layer. Furthermore, the nitride-based compound semiconductor device is characterized by having an auxiliary electrode provided above the third nitride-based compound semiconductor layer between the first main electrode and the control electrode, and electrically connected to the second main electrode.

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