Nitride semiconductor equipment

Abstract

To obtain a nitride-based semiconductor device with high voltage resistance and low on-resistance. [Solution] A nitride semiconductor device comprising a third nitride semiconductor layer 8 having a two-dimensional hole gas layer, wherein, as viewed from the control electrode 7 side, the third nitride semiconductor layer 8 on the first main electrode 6 side has a recessed portion 10, or multiple third nitride semiconductor layers 8 are intermittently provided on the second nitride semiconductor layer 4 and each of the multiple third nitride semiconductor layers 8 is electrically connected to the control electrode 7.

Description

Technical Field

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

Background Art

[0002] As a semiconductor device using a heterojunction of nitride semiconductors (GaN and its mixed crystal semiconductors), 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 the drain when it is off. 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 the gate in order to reduce the current collapse phenomenon.

[0003] As an example of a HEMT structure using a nitride semiconductor, for example, a HEMT structure using a PSJ (Polarization Super Junction) structure as described in Patent Document 1 is known. FIG. 14 is a cross-sectional view schematically showing a HEMT structure provided with a PSJ structure, and FIG. 15 is a plan view schematically showing a HEMT structure provided with a PSJ structure. In the nitride semiconductor device 100 shown in FIG. 14, for example, on a nitride semiconductor layer (first nitride semiconductor layer 3) made of undoped GaN, an undoped AlGaN (exactly Al 1-x Ga x N: 0 <x <1) is formed. As a result, a two-dimensional electron gas layer is generated in the first nitride semiconductor layer 3 near the interface between the first nitride semiconductor layer l 3 and the second nitride semiconductor layer 4.

[0004] On the second nitride semiconductor layer 4, a nitride semiconductor layer (third nitride semiconductor layer 8) is formed, which is made of undoped GaN similar to the first nitride semiconductor layer 3. A two-dimensional hole gas, in which holes are accumulated in a planar manner, is generated within the third nitride semiconductor layer 8 near the interface between the second nitride semiconductor layer 4 and the third nitride semiconductor layer 8.

[0005] By setting the gate electrode 7, which is provided on the third nitride semiconductor layer 8 via a P-type semiconductor layer 9, to a negative potential, the two-dimensional electron gas directly beneath the gate electrode 7 disappears, and the nitride semiconductor device 100 enters an off state. During turn-off, electrons constituting the two-dimensional electron gas move towards the drain electrode 6, and holes constituting the two-dimensional hole gas move towards the gate electrode 7. As a result, the electric field strength within the third nitride semiconductor layer 8 extending from the gate electrode 7 towards the drain electrode 6 is made nearly uniform, reducing localized increases in electric field strength directly beneath the gate electrode 7. This enables higher breakdown voltage and reduces the current collapse phenomenon. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-123161 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The region with the PSJ structure can have its electric field strength nearly uniform, allowing for higher voltage resistance. However, when the nitride-based semiconductor device is turned on, the concentration of the two-dimensional electron gas decreases, which increases the operating resistance and reduces the allowable current.

[0008] This disclosure has been made in view of the aforementioned problems and aims to provide a nitride-based semiconductor device that solves the above problems. [Means for solving the problem]

[0009] This disclosure has the following structure in order to solve the above-mentioned problems. This disclosure provides a first nitride-based semiconductor layer having a two-dimensional electron gas layer on top; a second nitride-based semiconductor layer provided on the first nitride-based semiconductor layer and having a band gap larger than the band gap of the first nitride-based semiconductor layer; a third nitride-based semiconductor layer provided on the second nitride-based semiconductor layer and made of a nitride-based semiconductor material having a band gap energy smaller than that of the second nitride-based semiconductor layer, wherein the third nitride-based semiconductor layer has a two-dimensional hole gas layer formed near the interface with the second nitride-based semiconductor layer; and P on the third nitride-based semiconductor layer. The third nitride semiconductor layer comprises a P-type 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 control electrode located between the first main electrode and the second main electrode and electrically connected to the P-type semiconductor layer, wherein, as viewed from the control electrode side, the third nitride semiconductor layer on the first main electrode side has a recessed portion, or multiple third nitride semiconductor layers are intermittently provided on the second nitride semiconductor layer, and each of the multiple third nitride semiconductor layers is electrically connected to the control electrode.

[0010] In addition, the present disclosure includes a first nitride semiconductor layer having a two-dimensional electron gas layer on the upper part, a second nitride semiconductor layer provided on the first nitride semiconductor layer and having a band gap larger than that of the first nitride semiconductor layer, and a third nitride semiconductor layer provided on the second nitride semiconductor layer and made of a nitride semiconductor material having a smaller band gap energy than that of the second nitride semiconductor layer. The third nitride semiconductor layer has a first two-dimensional hole gas layer generated near the interface with the second nitride semiconductor layer, a P-type semiconductor layer on the third nitride 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 control electrode between the first main electrode and the second main electrode and electrically connected to the P-type semiconductor layer. When viewed planarly, in a region formed from the end of the third nitride semiconductor layer closest to the first main electrode to directly below the control electrode to the length in the direction in which the control electrode extends, there is a region where no two-dimensional hole gas is generated or the concentration is low.

Advantages of the Invention

[0011] Since the present disclosure is configured as described above, it is possible to provide a nitride semiconductor device that substantially equalizes the electric field strength to increase the breakdown voltage while reducing the operating resistance value.

Brief Description of the Drawings

[0012] [Figure 1] It is a cross-sectional view showing the structure of the first embodiment of a nitride semiconductor device according to an embodiment of the present disclosure. [Figure 2] It is a plan view showing the structure of the first embodiment of a nitride semiconductor device according to an embodiment of the present disclosure. [Figure 3] It is a plan view showing the structure of the second embodiment of a nitride semiconductor device according to an embodiment of the present disclosure. [Figure 4] It is a plan view showing the structure of the third embodiment of a nitride semiconductor device according to an embodiment of the present disclosure. [Figure 5]It is a plan view showing the structure of the fourth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 6] It is a plan view showing the structure of the fifth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 7] It is a plan view showing the structure of a modified example of the fifth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 8] It is a cross-sectional view showing the structure of the sixth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 9] It is a plan view showing the structure of the sixth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 10] It is a cross-sectional view showing the structure of the seventh embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 11] It is a plan view showing the structure of the seventh embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 12] It is a cross-sectional view showing the structure of the eighth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 13] It is a plan view showing the structure of the eighth embodiment of the nitride semiconductor device according to the embodiment of the present disclosure. [Figure 14] It is a cross-sectional view showing the structure of a conventional nitride semiconductor device with a PSJ structure. [Figure 15] It is a plan view showing the structure of a conventional nitride semiconductor device with a PSJ structure.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, a nitride-based semiconductor device, which is an embodiment of the present disclosure, will be described with reference to the drawings. In the following drawings, identical or similar parts are denoted by the same 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, etc., may differ from those of reality. Therefore, specific dimensions should be determined by referring to the following explanation. Furthermore, it should be noted that there are parts where the relationships and ratios of dimensions differ between drawings. Furthermore, the embodiments described below illustrate nitride-based semiconductor devices for embodying the technical concept of this disclosure, and the technical concept of this disclosure does 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. In this disclosure, terms such as "top" and "bottom" are used for convenience of description, and even if they are provided on the side, they fall within the scope of the present invention if they are substantially identical to the constituent elements of this disclosure. Furthermore, "above" includes not only cases where it is formed in contact with the object, but also cases where it is formed through another layer. Also, in this disclosure, "connection" is not limited to direct connection; even if something such as a resistor is interposed between the two, if it is substantially the same as the constituent elements of this disclosure, it falls within the scope of the rights of the present invention.

[0014] The nitride-based semiconductor device 50 according to the embodiment of this disclosure, as shown in the cross-sectional view of the nitride-based semiconductor device 50 in Figure 1, comprises a substrate 1 made of sapphire, GaN, silicon, or silicon carbide, and a substrate provided on the substrate 1, such as AlN or Al x Ga 1-x N and Al y Ga 1-Y N is repeatedly stacked in a multilayer buffer, and Al has a gradient in composition. x Ga 1-xA buffer layer 2 having an N structure, a first nitride semiconductor layer 3 provided on the buffer layer 2 and composed of undoped GaN, and an undoped Al containing, for example, Al having a larger bandgap energy than the first nitride semiconductor layer 3 provided on the first nitride semiconductor layer 3 Z Ga 1-Z A second nitride semiconductor layer 4 composed of N (where Z>0), and a third nitride semiconductor layer 8 provided on the second nitride semiconductor layer 4 and composed of, for example, undoped GaN having a smaller bandgap energy than the second nitride semiconductor layer 4. In the first nitride semiconductor layer 3 near the interface between the first nitride semiconductor layer 3 and the second nitride semiconductor layer 4, a two-dimensional electron gas layer is generated by spontaneous polarization or piezoelectric polarization or both. Also, in the third nitride semiconductor layer 8 near the interface between the second nitride semiconductor layer 4 and the third nitride semiconductor layer 8, a two-dimensional hole gas layer (two-dimensional positive hole gas layer) is generated by spontaneous polarization or piezoelectric polarization or both.

[0015] The source electrode 5 and the drain electrode 6 are formed on the first nitride semiconductor layer 3 or the second nitride semiconductor layer 4, and are composed of a material that makes an ohmic contact with the two-dimensional electron gas layer, and are composed of, for example, a stacked structure of Ti / Au. Note that the drain electrode 6 and the source electrode 5 do not contact the third nitride semiconductor layer 8 and are not connected to the two-dimensional hole gas layer in the third nitride semiconductor layer 8.

[0016] A gate electrode 7 electrically connected to the third nitride semiconductor layer 8 is provided on the second nitride semiconductor layer 4 between the source electrode 5 and the drain electrode 6. Here, on the second nitride semiconductor layer 4 in FIG. 1, a third nitride semiconductor layer 8, a P-type semiconductor layer 9 composed of, for example, p-GaN or NiO on the third nitride semiconductor layer 8, and a gate electrode 7 on the P-type semiconductor layer 9 are formed. The gate electrode 7 is composed of a material that makes an ohmic contact with the P-type semiconductor layer 9, and is composed of, for example, a stacked structure of Ni / Au. The portion of the third nitride semiconductor layer 8 that extends toward the drain electrode 6 side from the gate electrode 7 or the P-type semiconductor layer 9 (the portion with length B in Figure 2) is sometimes called a PSJ structure (Polarization Super Junction).

[0017] Here, within the area enclosed by length B of the PSJ structure (in Figure 2, the boundary on the drain electrode 6 side of this area is shown by a dotted line), multiple recesses (grooves) 10 with length A extending from the drain electrode 6 side towards the gate electrode 7 side are provided in the direction in which the gate electrode 7 extends (Y direction in Figure 2). Looking from the gate electrode 7 closest to the source electrode 5, within the area enclosed by length B of the PSJ structure, multiple recesses (grooves) 10 with length A extending from the drain electrode 6 side towards the gate electrode 7 side (X direction in Figure 2) are provided in the Y direction in Figure 2. In the area enclosed by length A in Figure 2, the portion 8a where the PSJ structure of the third nitride semiconductor layer 8 is provided and the recesses (grooves) 10 are alternately and repeatedly formed in the Y direction.

[0018] The recessed portion (groove) 10 is a region where at least a portion of the third nitride-based semiconductor layer 8 is not provided, and is a region where a two-dimensional hole gas layer does not form or where the two-dimensional hole gas layer is small. The recessed portion (groove) 10 is, for example, a portion in which a groove or hole is formed that does not penetrate the third nitride-based semiconductor layer 8, or a portion in which a groove or hole that penetrates the third nitride-based semiconductor layer 8 is provided. In the recessed portion (groove) 10, at least a portion of the thickness of the third nitride-based semiconductor layer 8 may remain, and it may be a region where a two-dimensional hole gas layer does not form or where the concentration of the two-dimensional hole gas layer is small. In this case, it is possible to suppress the occurrence of crystal defects etc. on the upper part of the second nitride-based semiconductor layer 4 directly below the recessed portion (groove) 10, and characteristics such as current collapse and on-resistance can be improved.

[0019] The P-type semiconductor layer 9 and the gate electrode 7 are provided on the second nitride-based semiconductor layer 4, which is on the source electrode 5 side of the third nitride-based semiconductor layer 8, and the P-type semiconductor layer 9 and the third nitride-based semiconductor layer 8 may be electrically connected. Alternatively, as shown in Figure 1, the P-type semiconductor layer 9 and the gate electrode 7 may be stacked on the third nitride-based semiconductor layer 8.

[0020] Also, the maximum length B of the PSJ structure max Within this range, the area (E × B) is defined by being enclosed by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 2). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low.

[0021] When a potential above a threshold is applied to the gate electrode 7, the depletion layer directly beneath the gate electrode 7 decreases, the two-dimensional electron gas layer becomes conductive, and the nitride semiconductor device 50 turns on. At this time, a two-dimensional hole gas layer is formed within the third nitride semiconductor layer 8, canceling out electrons trapped on the surface of the second nitride semiconductor layer 4 directly beneath and near the third nitride semiconductor layer 8. This reduces the current collapse phenomenon of the nitride semiconductor device 50. In this case, the concentration of the two-dimensional electron gas layer directly beneath the PSJ structure in portion 8a decreases to some extent. However, in the nitride semiconductor device 50, the two-dimensional hole gas in the recess (groove) 10 is absent or less than in portion 8a where the PSJ structure is provided. Therefore, the concentration of the two-dimensional electron gas layer directly beneath the recess (groove) 10 can be increased relatively. As a result, the on-resistance of the nitride semiconductor device 50 can be reduced.

[0022] On the other hand, when an off signal (e.g., a negative potential) is applied to the gate electrode 7, the carriers in the two-dimensional electron gas layer directly beneath the gate electrode 7 are depleted, and the nitride semiconductor device 50 is turned off. Holes in the two-dimensional hole gas layer within the third nitride semiconductor layer 8 move to the gate electrode 7 and are discharged, and the concentration of the two-dimensional hole gas layer within the third nitride semiconductor layer 8 decreases. As a result, the electric field strength in the second nitride semiconductor layer 4 beneath the third nitride semiconductor layer 8 in the direction from the gate electrode 7 to the drain electrode 6 (X direction in Figure 2) is made nearly uniform. Therefore, localized increases in electric field strength near the gate electrode 7 are suppressed, and the breakdown voltage of the nitride semiconductor device can be increased. When the nitride semiconductor device 50 is in the off state, the electric field on the surface of the second nitride semiconductor layer 4 directly beneath the portion 8a where the PSJ structure is provided is substantially homogenized due to the influence of the electric field strength within the third nitride semiconductor layer 8. The depression (groove) 10 is, for example, sandwiched between the region of the second nitride semiconductor layer 4 directly beneath the portion 8a where the PSJ structure is provided in the Y direction of Figure 2. The electric field strength on the surface of the depression (groove) 10 is a valley, but due to the influence of the electric field in the portion where the PSJ structure is provided, the electric field strength on the surface of the depression (groove) 10 rises and becomes relatively smooth. Therefore, the nitride semiconductor device 50 can suppress electrons trapped on the surface of the second nitride semiconductor layer 4, etc., and reduce the current collapse phenomenon.

[0023] From the above, it is possible to provide a nitride-based semiconductor device 50 that reduces on-resistance while achieving high voltage resistance by making the electric field strength nearly uniform.

[0024] In the range of length B of the PSJ structure in Figure 2, it is desirable that the recess (groove) 10 be located on the drain electrode 6 side compared to the gate electrode 7 side. This allows the electric field concentration on the gate electrode 7 side to be mitigated by the PSJ structure, while increasing the concentration of the two-dimensional electron gas layer directly below the recess (groove) 10 on the drain electrode 6 side where the PSJ structure is absent, thereby suppressing an increase in on-resistance. For example, in the direction in which the PSJ structure extends (the X direction in Figure 2), the maximum length B of the PSJ structure... max When the length of the region where the recessed portion (groove) 10 is provided is A, then A / Bmax For example, this can be greater than 1 / 3 and less than 1. Also, when the width of the recess (groove) 10 (length in the Y direction in Figure 2) is C and the width of the extended portion of the PSJ structure (length in the Y direction in Figure 2) is D, the width D may be greater than the width C. This makes it possible to provide a nitride-based semiconductor device 50 that reduces on-resistance while achieving high voltage resistance by making the electric field strength approximately uniform.

[0025] <Second Embodiment> Figure 3 is a plan view showing a second embodiment of the nitride-based semiconductor device 51 of the present disclosure. Although not particularly limited, as shown in the plan view of Figure 3, a recess (groove) 10 is provided in the third nitride-based semiconductor 8 extending from the drain electrode 6 side to the gate electrode 7 side. The width of the extended portion 8a of the PSJ structure of the third nitride-based semiconductor 8 (width D in the Y direction of Figure 3) narrows from the gate electrode 7 side to the drain electrode 6 side (X direction in Figure 3). The width of the groove (width C in the Y direction of Figure 3) of the recess (groove) 10 widens from the gate electrode 7 side to the drain electrode 6 side (X direction in Figure 3). In the nitride-based semiconductor device 51, the maximum length B of the PSJ structure is also max Within the area enclosed by the rectangle (in Figure 3, the boundary on the drain electrode 6 side of this area is shown by a dotted line), there are multiple recesses (grooves) 10 of length A extending from the drain electrode 6 side towards the gate electrode 7 side, in the direction in which the gate electrode 7 extends (the Y direction in Figure 3). Also, the maximum length B of the PSJ structure max Within this range, the area (E × B) is defined by being enclosed by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 3). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low.

[0026] Therefore, even in the nitride-based semiconductor device 51 of the second embodiment, it is possible to provide a nitride-based semiconductor device that suppresses the increase in on-resistance while reducing the current collapse phenomenon. Also, in Figure 3, the ratio of the non-extended portion of the PSJ structure on the drain electrode 6 side (width C / width C + width D) is greater than the ratio on the gate electrode 7 side (width C / width C + width D), for example, the ratio on the drain electrode 6 side is greater than that of the semiconductor device of the first embodiment. Therefore, the nitride-based semiconductor device 51 can further reduce on-resistance. Furthermore, in Figure 3, the ratio of the extended portion 8a of the PSJ structure on the gate electrode 7 side (width D / width C + width D) is greater than the ratio on the drain electrode 6 side (width D / width C + width D), for example, the ratio on the gate electrode 7 side is greater than that of the semiconductor device of the first embodiment. As a result, the two-dimensional electron gas layer directly beneath the gate electrode 7 side is more easily depleted, and the electric field distribution in the Y direction can be made more uniform. Furthermore, the end of the PSJ structure on the drain electrode 6 side is thinner than the portion of the PSJ structure on the gate electrode 7 side, which mitigates electric field concentration directly beneath the end of the gate electrode 7. From the above, it is possible to provide a nitride-based semiconductor device 51 that achieves high voltage resistance by making the electric field strength nearly uniform, while further reducing on-resistance.

[0027] <Third Embodiment> Figure 4 is a plan view showing a third embodiment of the nitride-based semiconductor device 52 of the present disclosure. Although not particularly limited, as shown in the plan view of Figure 4, a recess (groove) 10 is provided extending from the drain electrode 6 side to the gate electrode 7 side. The groove of the recess (groove) 10 widens the width of the extended portion 8a of the PSJ structure (width D in the Y direction of Figure 4) from the gate electrode 7 side to the drain electrode 6 side (X direction in Figure 4). On the other hand, the width of the recess (groove) 10 (width C in the Y direction of Figure 4) narrows from the gate electrode 7 side to the drain electrode 6 side (X direction in Figure 4).

[0028] In the nitride semiconductor device 52 of the third embodiment, it is possible to provide a nitride semiconductor device that suppresses the increase in on-resistance while reducing the current collapse phenomenon. Furthermore, in the range of length A in Figure 4, the ratio of the non-extended portion of the PSJ structure on the gate electrode 7 side (width C / width C + width D) is greater than the ratio on the drain electrode 6 side (width C / width C + width D). For example, the ratio on the gate electrode 7 side is greater than the ratio on the gate electrode 7 side in the nitride semiconductor device 50 of the first embodiment. Therefore, the nitride semiconductor device 52 can increase the concentration of the two-dimensional electron gas layer on the gate electrode 7 side. Also, in the range of length A in Figure 4, the ratio of the extended portion 8a of the PSJ structure (width D / width C + width D) is large on the drain electrode 6 side, and is greater than, for example, the ratio on the drain electrode 6 side (width D / width C + width D) in the nitride semiconductor device 50 of the first embodiment. Therefore, it is possible to provide a nitride semiconductor device 52 that reduces on-resistance while making the electric field strength more nearly uniform and achieving a higher breakdown voltage.

[0029] <Fourth Embodiment> Figure 5 is a plan view showing a fourth embodiment of the nitride-based semiconductor device 53 of the present disclosure. Although not particularly limited, as shown in the plan view of Figure 5, a recess (groove) 10 is provided in the third nitride-based semiconductor 8 from the drain electrode 6 side toward the gate electrode 7 side. As a result, toward the gate electrode 7 side, the width of the extended portion 8a of the PSJ structure (width D in Figure 5) narrows toward the gate electrode 7. And toward the gate electrode 7, the width of the recess (groove) 10 (width C in Figure 5) widens. On the other hand, on the drain electrode 6 side, the width of the portion 8a of the PSJ structure that extends toward the drain electrode 6 (width D in Figure 5) is narrower, while the width of the recessed portion (groove) 10 (width C in Figure 5) is wider. In other words, the width of the extended portion 8a of the PSJ structure (width D in Figure 5) is widest on the way from the drain electrode 6 side to the gate electrode 7 side, and the recessed portion (groove) 10 is narrowest in the corresponding portion (the portion sandwiched between the widest portion 8a). Then, towards the drain electrode 6 side and the gate electrode 7 side, the width of the extended portion 8a of the PSJ structure (width D in Figure 5) narrows, and the width of the recessed portion (groove) 10 (width C in Figure 5) widens.

[0030] In nitride-based semiconductor devices 53, the maximum length B of the PSJ structure is also max Within the area enclosed by the box (in Figure 5, the boundary on the drain electrode 6 side of this area is shown by a dotted line), there are multiple recesses (grooves) 10 with length A extending from the drain electrode 6 side towards the gate electrode 7 side, in the direction of extension of the gate electrode 7 (the Y direction in Figure 5). Also, the maximum length B of the PSJ structure max Within this range, the area (E × B) is defined by being enclosed by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 5). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low.

[0031] The recessed portion (groove) 10 is formed by etching the third nitride-based semiconductor layer 14. Therefore, product variations are likely to occur in the ratio of the recessed portion (groove) 10 to the PSJ structure portion 8a. Since the depletion layer spreads from the gate electrode 7 side, this variation is likely to lead to variations in breakdown voltage and on-resistance. Therefore, the width D of the PSJ structure portion 8a is gradually increased as it progresses from the gate electrode 7 side towards the drain electrode 6 side. This makes the depletion layer spread more easily on the drain electrode 6 side than on the gate electrode 7 side, suppressing variations in breakdown voltage. Then, the width D of the PSJ structure portion 8a is gradually decreased from the middle of the PSJ structure portion 8a that progresses from the gate electrode 7 side towards the drain electrode 6 side. This increases the concentration of the two-dimensional electron gas layer on the drain electrode 6 side, suppressing variations in on-resistance. Therefore, it is possible to provide a nitride-based semiconductor device 53 that achieves high voltage resistance by making the electric field strength nearly uniform, while further reducing on-resistance and suppressing variations in on-resistance.

[0032] <Fifth Embodiment> Figure 6 is a plan view showing a fifth embodiment of the nitride semiconductor device 54 of the present disclosure. Although not particularly limited, as shown in the plan view of Figure 6, the drain electrode 6 side end of adjacent PSJ structure portions 8a in the Y direction is connected by a connection portion 8b of the third nitride semiconductor layer 8. The connection portion 8b of the third nitride semiconductor layer 8 is also a PSJ structure portion. The nitride semiconductor device 54 has a structure in which elongated recesses (holes) 10 in the X direction are provided in the PSJ structure portion of the third nitride semiconductor layer 8. Within the area enclosed by the length B of the PSJ structure, multiple recesses (holes) 10 with a length A extending from the drain electrode 6 side to the gate electrode 7 side are provided in the direction in which the gate electrode 7 extends (Y direction in Figure 6). Also, the maximum length B of the PSJ structure max Within this range, the area (E × B) is defined by being enclosed by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 6). max Rather than the above, it is desirable that the area where the two-dimensional hole gas layer is generated in the third nitride-based semiconductor layer 8 is small, or that there are regions where the hole concentration of the two-dimensional hole gas layer is low. Therefore, multiple recesses (holes) 10 with length A in the X direction are provided in the third nitride semiconductor layer 8. The area around the recesses (holes) 10 is surrounded by PSJ structure portions 8a and 8b.

[0033] The area directly beneath the recess (hole) 10 has a relatively high concentration of the two-dimensional electron gas layer, which can reduce the on-resistance of the nitride semiconductor device 54. Furthermore, the drain electrode 6 side of the PSJ structure is a location where electric field concentration is relatively likely to occur. By connecting the ends of adjacent PSJ structure portions 8a in the Y direction at the connection portion 8b of the third nitride semiconductor layer 8, electric field concentration at the drain electrode 6 side of the PSJ structure can be mitigated. Therefore, the nitride-based semiconductor device 54 can achieve a more uniform electric field strength, thereby increasing its breakdown voltage while reducing its on-resistance.

[0034] It is also clear that, in the nitride-based semiconductor devices of the first to fourth embodiments, the ends of adjacent PSJ structures 8a in the Y direction may be connected at the connection portion 8b of the third nitride-based semiconductor layer 8, similar to the nitride-based semiconductor device of the fifth embodiment.

[0035] Figure 7 is a plan view showing a modified example of the fifth embodiment of the nitride-based semiconductor device 55 of the present disclosure. Although not particularly limited, as shown in the plan view of Figure 7, the recessed portion (hole) 10 may be not only like the hole in Figure 6, but may also consist of multiple circular recessed portions (holes) 10. Furthermore, as shown in the plan view of Figure 7, the recessed portions (holes) 10 may be arranged alternately in multiple locations. In Figure 7, the recessed portions (holes) 10 are evenly distributed in the plane, but many recessed portions (holes) 10 may be arranged on the gate electrode 7 side or the drain electrode 6 side of the PSJ structure.

[0036] <Sixth Embodiment> Figure 8 is a cross-sectional view showing a sixth embodiment of the nitride-based semiconductor device 56 of the present disclosure, and Figure 9 is a plan view showing a sixth embodiment of the nitride-based semiconductor device 56 of the present disclosure. Although not particularly limited, a field plate 11 may be provided at the drain electrode 6 side end of the PSJ structure third nitride semiconductor layer 8, as shown in the cross-sectional view of Figure 8. The field plate 11 extends further toward the drain electrode 6 side than the end of the third nitride semiconductor layer 8 and is formed on the insulating film 12. The field plate 11 may be provided not on the end side of the PSJ structure portion 8a, but on the side of the PSJ structure portion 8a along the recess (groove) 10. Alternatively, a field plate 11 may be provided on the recessed portion (groove) 10. For example, a field plate 11 may be provided on the recessed portion (groove) 10 on the gate electrode 7 side.

[0037] The field plate 11 is formed of a metal or conductive polysilicon, etc. The field plate 11 may be connected to the third nitride-based semiconductor layer 8. As shown in the plan view of Figure 8, the width (width in the Y direction) of the field plate 11 is wider than the width (width in the Y direction) of the portion 8a of the PSJ structure opposite it, and the field plate 11 may extend outward from the third nitride-based semiconductor layer 8.

[0038] The field plate 11 may also be electrically connected to the gate electrode 7. By providing the field plate 11, electric field concentration at the drain electrode 6 side end of the third nitride semiconductor layer 8 can be mitigated. In particular, since the recessed portion (groove) 10 extends from the drain electrode 6 side, providing the field plate 11 at the drain electrode 6 side end of the PSJ structure portion 8a can further mitigate electric field concentration on the drain electrode 6 side of the PSJ structure. Furthermore, for example, as shown in Figure 9, by making the width of the field plate 11 (width in the Y direction) larger than the width of the drain electrode 6 side of the PSJ structure portion 8a (width in the Y direction), and providing the field plate 11 toward the recessed portion (groove) 10, electric field concentration on the drain electrode 6 side of the PSJ structure can be further mitigated. Therefore, the nitride-based semiconductor device 56 can suppress the increase in on-resistance, further reduce electron trapping, and further reduce the current collapse phenomenon.

[0039] It is also clear that in the first to fifth embodiments, a field plate 11 may be provided, similar to the sixth embodiment. Maximum length B of PSJ structure max Within the enclosed area, multiple recesses (grooves) 10 with length A extending from the drain electrode 6 side to the gate electrode 7 side are provided in the direction of extension of the gate electrode 7 (Y direction in Figure 9). Furthermore, the maximum length B of the PSJ structure max Within this range, the area (E × B) is defined by being enclosed by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 9). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low. Therefore, the nitride-based semiconductor device 56 can achieve a more uniform electric field strength, thereby increasing its breakdown voltage while reducing its on-resistance.

[0040] <Seventh Embodiment> Figure 10 is a cross-sectional view showing a seventh embodiment of the nitride-based semiconductor device 57 of the present disclosure, and is a cross-sectional view taken at the FF in the plan view of Figure 11. Figure 11 is a plan view showing a seventh embodiment of the nitride-based semiconductor device 57 of the present disclosure. Note that in Figure 11, the gate electrode 7c, the P-type semiconductor layer 9c, and the field plate 13c are omitted.

[0041] While not particularly limited, as shown in the cross-sectional view of Figure 10, the PSJ structure of the third nitride semiconductor layer 8 is provided with recesses (grooves) 10 in the direction of extension of the gate electrode 7 (Y direction). For example, the recesses (grooves) 10 divide the third nitride semiconductor layer into multiple sections in the X direction, and spaced-apart third nitride semiconductor layers 8c are provided on the second nitride semiconductor layer 4. In other words, a divided PSJ structure is formed on the second nitride semiconductor layer 4.

[0042] Each of the third nitride semiconductor layers 8c is provided with a P-type semiconductor layer 9c and a gate electrode 7c, and each third nitride semiconductor layer 8c extends toward the drain electrode 6 side than its corresponding P-type semiconductor layer 9c. Each gate electrode 7c is electrically connected to the gate electrode 7. Here, the length B of the PSJ structure of the third nitride semiconductor layer 8 that extends toward the drain electrode 6 side than the P-type semiconductor layer 9 in Figure 1 is approximately the same as the length B from the end of the third nitride semiconductor layer 8c on the drain electrode 6 side, where the gate electrode 7 on the source electrode 5 side and the third nitride semiconductor layer 8c are connected, to the end of the third nitride semiconductor layer 8c on the drain electrode 6 side, where it is connected to the gate electrode 7, in Figure 11.

[0043] Therefore, the nitride semiconductor device 57 has a structure in which a third nitride semiconductor layer 8c, intermittently provided on the second nitride semiconductor layer 4, is connected to the gate electrode G. The entire PSJ structure of the nitride semiconductor device 57 is within the range of length B in Figures 10 and 11, and a recess (groove) 10 is provided within the range of length A. Furthermore, looking from the gate electrode 7 closest to the source electrode 5, multiple recesses (grooves) 10 extending in the Y direction in Figure 11 are provided from the drain electrode 6 side (X direction in Figure 11) to the gate electrode 7 side (X direction in Figure 11), from the end on the drain electrode 6 side where the gate electrode 7 closest to the source electrode 5 and the third nitride semiconductor layer 8c are connected, to the end of the PSJ structure portion of the third nitride semiconductor layer closest to the drain electrode 6 side that is connected to the gate electrode 7 (range of length B). The maximum length B of the PSJ structure portion in the X direction is... max Within this range, the area (E × B) is defined by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 11). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low.

[0044] Furthermore, in the X direction, at least one of the multiple third nitride semiconductor layers 8c has a field plate 13c at the drain electrode 6 side end of the third nitride semiconductor layer 8c. Incidentally, in the nitride semiconductor device 57 of Figure 10, the field plate 13c is provided on all of the multiple third nitride semiconductor layers 8c.

[0045] The field plate 13c is formed of a metal or conductive polysilicon, etc. The field plate 13c may be connected to the third nitride-based semiconductor layer 8c. The field plate 13c may extend beyond the edge of the third nitride-based semiconductor layer 8c toward the drain electrode 6.

[0046] When a third nitride semiconductor layer is provided, the concentration of the two-dimensional electron gas layer directly beneath the third nitride semiconductor layer decreases. For example, the third nitride semiconductor layer 8, which extends further toward the drain electrode 6 than the P-type semiconductor layer 9 in Figure 1, is divided into multiple layers, and the P-type semiconductor layers 9c provided on each of these third nitride semiconductor layers are connected to the gate electrode 7. Here, by extending each of the third nitride semiconductor layers 8c directly beneath the P-type semiconductor layer 9c toward the drain electrode 6, each of the third nitride semiconductor layers 8c functions as a PSJ structure. Therefore, the nitride semiconductor device 57 can increase the electric field borne by each PSJ structure, and reduce the electric field peak from the gate electrode 7 to the drain electrode 6.

[0047] Furthermore, the concentration of the two-dimensional electron gas layer directly below the recess (groove) 10 between the third nitride-based semiconductor layer 8c can be made relatively high. From the above, it is possible to provide a nitride-based semiconductor device 57 that achieves high voltage resistance by making the electric field strength nearly uniform, while further reducing on-resistance.

[0048] In addition, in the first to sixth embodiments, a recess (groove) 10 may be provided in the Y direction, similar to the seventh embodiment. For example, it is clear that the third nitride semiconductor layer 8 may be divided, and a P-type semiconductor layer 9c and a gate electrode 7c may be provided on each of the divided third nitride semiconductor layers 8c, and the gate electrode 7c may be electrically connected to the gate electrode 7.

[0049] Furthermore, although the field plate 13c is provided on all of the divided third nitride-based semiconductor layers 8c in Figure 10, the field plate 13c does not need to be provided on some of the divided third nitride-based semiconductor layers 8c.

[0050] <Eighth Embodiment> Figure 12 is a cross-sectional view showing an eighth embodiment of the nitride-based semiconductor device 58 of the present disclosure, and is a cross-sectional view taken at HH in the plan view of Figure 13. Figure 13 is a plan view showing an eighth embodiment of the nitride-based semiconductor device 58 of the present disclosure. Note that in Figure 13, the gate electrode 7c, the P-type semiconductor layer 9c, and the field plate 13c are omitted.

[0051] Although not particularly limited, as shown in the cross-sectional view of Figure 12, the PSJ structure of the third nitride semiconductor layer 8 is provided with recesses (grooves) 10 that extend in the direction in which the gate electrode 7 extends (Y direction) and in the direction from the gate electrode 7 toward the drain electrode 6 (X direction). For example, the third nitride semiconductor layer is divided into multiple sections by grooves provided in the X and Y directions as shown in Figure 13, and spaced-apart third nitride semiconductor layers 8c are provided on the second nitride semiconductor layer 4.

[0052] Incidentally, the length B of the PSJ structure of the third nitride semiconductor layer 8 that extends from the gate electrode 7 towards the drain electrode 6 in Figure 1 is approximately the same as the length B from the end of the third nitride semiconductor layer 8c on the drain electrode 6 side where the gate electrode 7 and the third nitride semiconductor layer 8c are connected in Figure 13 to the end of the third nitride semiconductor layer 8c on the drain electrode 6 side where it is connected to the gate electrode 7.

[0053] Each of the third nitride semiconductor layers 8c is provided with a P-type semiconductor layer 9c and a gate electrode 7c, with the third nitride semiconductor layer 8c extending further toward the drain electrode 6 than the P-type semiconductor layer 9c. Each gate electrode 7c is electrically connected to the gate electrode 7.

[0054] Therefore, the nitride semiconductor device 57 has a structure in which a third nitride semiconductor layer 8c, intermittently provided on the second nitride semiconductor layer 4, is connected to the gate electrode 7. The entire PSJ structure of the nitride semiconductor device 58 is within the range of length B in Figures 12 and 13, and a recess (groove) 10 is provided within the range of length A. In the PSJ structure portion (range of length B) of the third nitride semiconductor layer 8c that extends toward the drain electrode 6 and connects to the gate electrode 7 when viewed from the gate electrode 7 closest to the source electrode 5, multiple recesses (grooves) 10 extending in the Y direction in Figure 13 are provided from the drain electrode 6 side to the gate electrode 7 side (X direction in Figure 13). The maximum length B of the PSJ structure of the third nitride semiconductor layer 8c that extends toward the drain electrode 6 and connects to the gate electrode when viewed from the gate electrode 7 closest to the source electrode 5 is... maxWithin this range, the area (E × B) is defined by the length of the gate electrode 7 (finger length of the gate electrode 7) E in the direction in which the gate electrode 7 extends (Y direction in Figure 13). max Rather than the above, it is desirable that the third nitride-based semiconductor layer 8 has a smaller area where a two-dimensional hole gas layer is generated or a region where the hole concentration of the two-dimensional hole gas layer is low.

[0055] Furthermore, in the X direction, at least one of the multiple third nitride semiconductor layers 8c has a field plate 13c at the end of the third nitride semiconductor layer 8c that is extended beyond the P-type semiconductor layer 9c. Incidentally, in the nitride semiconductor device 57 shown in Figure 12, the field plate 13c is provided on all of the multiple third nitride semiconductor layers 8c.

[0056] The field plate 13c is formed of a metal or conductive polysilicon, etc. The field plate 13c may be connected to the third nitride-based semiconductor layer 8c. The field plate 13c extends toward the drain electrode 6 side beyond the edge of the third nitride-based semiconductor layer 8c and may be formed on an insulating film.

[0057] When a third nitride-based semiconductor layer is provided, the concentration of the two-dimensional electron gas layer directly beneath the third nitride-based semiconductor layer decreases. The third nitride-based semiconductor layer 8 in Figure 1 is provided with recesses (grooves) 10 in the X and Y directions. For example, the PSJ structure portion of the third nitride-based semiconductor layer extended toward the drain electrode 6 is divided into multiple parts in the X and Y directions, and a P-type semiconductor layer 9c is provided on each of the divided third nitride-based semiconductor layers 8c, and the P-type semiconductor layer 9c is connected to the gate electrode 7. Here, the third nitride-based semiconductor layer 8c is extended toward the drain electrode 6 side than the P-type semiconductor layer 9c. As a result, each of the third nitride-based semiconductor layers 8c functions as a PSJ structure. Therefore, the nitrogen-based semiconductor device 58 can increase the electric field borne by each PSJ structure, and the electric field peak from the gate electrode 7 to the drain electrode 6 can be reduced.

[0058] Furthermore, the concentration of the two-dimensional electron gas layer directly beneath the third nitride-based semiconductor layer 8c can be made relatively high. From the above, it is possible to provide a nitride-based semiconductor device 58 that achieves high voltage resistance by making the electric field strength nearly uniform, while further reducing on-resistance.

[0059] Furthermore, in the nitride-based semiconductor devices of the first to sixth embodiments, recesses (grooves) 10 may be provided in the X and Y directions, similar to the nitride-based semiconductor device of the eighth embodiment. For example, it is clear that the third nitride-based semiconductor layer 8 may be divided, and a P-type semiconductor layer 9c and a gate electrode 7c may be provided on each of the divided third nitride-based semiconductor layers 8c, and the gate electrode 7c may be electrically connected to the gate electrode 7. Furthermore, although the field plate 13c is provided on all of the divided third nitride-based semiconductor layers 8c, the field plate 13c does not need to be provided on some of the divided third nitride-based semiconductor layers 8c. [Explanation of Symbols]

[0060] 1 circuit board 2 buffer layers 3. First Nitride Semiconductor Layer 4. Second Nitride Semiconductor Layer 5. Source electrode (second main electrode) 6. Second drain electrode (first main electrode) 7 Airports 8. Third Nitride Semiconductor Layer 9 P-type semiconductor layer 10 Recessed area

Claims

1. A first nitride-based semiconductor layer having a two-dimensional electron gas layer on top, A second nitride-based semiconductor layer is provided on the first nitride-based semiconductor layer and has a band gap larger than the band gap of the first nitride-based semiconductor layer, A third nitride-based semiconductor layer is provided on the second nitride-based semiconductor layer and is made of a nitride-based semiconductor material having a smaller bandgap energy than the second nitride-based semiconductor layer, and the third nitride-based semiconductor layer has a two-dimensional hole gas layer formed near the interface with the second nitride-based semiconductor layer, The P-type semiconductor layer on the third nitride-based 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 control electrode is located between the first main electrode and the second main electrode and is electrically connected to the P-type semiconductor layer, Equipped with, A nitride semiconductor device characterized in that, as viewed from the control electrode side, the third nitride semiconductor layer on the first main electrode side has a recessed portion, or is provided intermittently in multiples on the second nitride semiconductor layer, and each of the multiple third nitride semiconductor layers is electrically connected to the control electrode.

2. A first nitride-based semiconductor layer having a two-dimensional electron gas layer on top, A second nitride-based semiconductor layer is provided on the first nitride-based semiconductor layer and has a band gap larger than the band gap of the first nitride-based semiconductor layer, A third nitride semiconductor layer is provided on the second nitride semiconductor layer and is made of a nitride semiconductor material having a smaller bandgap energy than the second nitride semiconductor layer, and the third nitride semiconductor layer has a first two-dimensional hole gas layer formed near the interface with the second nitride semiconductor layer, The P-type semiconductor layer on the third nitride-based 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 control electrode is located between the first main electrode and the second main electrode and is electrically connected to the P-type semiconductor layer, Equipped with, A nitride-based semiconductor device characterized in that, when viewed in plan view, in a region formed from the end of the third nitride-based semiconductor layer closest to the first main electrode to directly below the control electrode, there is a region where two-dimensional hole gas is not generated or has a low concentration.

3. Viewed in two dimensions, The nitride semiconductor device according to claim 1, characterized in that the recesses of the third nitride semiconductor layer, or the plurality of third nitride semiconductor layers intermittently provided on the second nitride semiconductor layer, are aligned in the direction of extension of the control electrode.

4. Viewed in two dimensions, The nitride semiconductor device according to claim 1, characterized in that the recesses of the third nitride semiconductor layer, or the third nitride semiconductor layer provided intermittently on the second nitride semiconductor layer, are arranged in the direction from the control electrode to the first main electrode.

5. Viewed in two dimensions, In the range where the maximum length of the third nitride-based semiconductor layer extending from the control electrode toward the first main electrode is in the direction of extension of the control electrode, The nitride-based semiconductor device according to claim 1, characterized in that the ratio of the recessed portion is higher on the control electrode side than on the first main electrode side.

6. Viewed in two dimensions, In the range where the maximum length of the third nitride-based semiconductor layer extending from the control electrode toward the first main electrode is in the direction of extension of the control electrode, The nitride-based semiconductor device according to claim 1, characterized in that the ratio of the recessed portion is higher on the first main electrode side than on the control electrode side.

7. The width of the third nitride-based semiconductor layer extending from the control electrode to the first main electrode is: A widening portion that extends from the control electrode side toward the first main electrode side, The nitride semiconductor device according to claim 1 or 2, characterized in that it has a narrowing portion which is located on the first main electrode side of the widening portion and narrows toward the first main electrode side from the control electrode side.

8. The nitride-based semiconductor device according to claim 1 or 2, characterized in that a field plate is provided at the end of the third nitride-based semiconductor layer on the first main electrode side.

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