JP2009177028A - Semiconductor apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor apparatus including a Schottky barrier diode obtaining high voltage resistance and using a nitride semiconductor. <P>SOLUTION: A semiconductor apparatus includes: an n+ type semiconductor substrate 1; an n- type drift region 2 formed on the upper surface of the n+ type semiconductor substrate 1; an anode electrode 3 formed on the upper surface of the n- type drift region 2 and forming a Schottky junction A with the n- type drift region 2; and a cathode electrode 4 electrically connected to the n+ type semiconductor substrate 1. The semiconductor apparatus also includes trenches 5 selectively formed on the surface of the n- type drift region 2, and the trench 5 is burred by the anode electrode 3. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device, and more particularly to a Schottky barrier diode (SBD) using a nitride semiconductor.

  Nitride semiconductors such as gallium nitride (GaN) have a larger band gap than silicon (Si) and have a high critical electric field, so that it is easy to realize a small and high breakdown voltage device. By using a nitride semiconductor, an on-resistance can be lowered and a low-loss element can be realized in a power control semiconductor device used for electrical equipment, communication equipment, and the like. In particular, in the vertical Schottky barrier diode, the on-resistance can be lowered and the chip area can be reduced.

  If the drift region is formed thick and the impurity concentration is low in order to realize a high breakdown voltage device with a normal Schottky barrier diode, the on-resistance increases. Thus, the on-resistance and breakdown voltage of the Schottky barrier diode are in a trade-off relationship. In order to pass a large current through such an element, it is necessary to increase the chip area.

  In the Schottky barrier diode, a depletion layer extends from the Schottky junction between the anode electrode and the drift region. In the depletion layer extending from the end portion of the anode electrode, a portion having a large curvature may occur, and the electric field may concentrate. As a result, the leakage current flowing through the Schottky junction increases, and the breakdown voltage tends to decrease. If the drift region is thick and the impurity concentration is low in order to suppress this drop in breakdown voltage, the on-resistance increases as described above.

  In a conventional Schottky barrier diode using silicon, a p-type doped guard ring region is provided at the end of the anode electrode on the surface of the n-type drift region in order to suppress a decrease in breakdown voltage due to such electric field concentration. Yes. By forming a deep guard ring region by impurity diffusion, the radius of curvature of the depletion layer at the end of the anode electrode is increased, and electric field concentration can be mitigated. However, since a nitride semiconductor such as gallium nitride (GaN) has a small diffusion constant, it is difficult to form a deep guard ring region. Therefore, it is difficult to realize a guard ring structure similar to a Schottky barrier diode using silicon. Thus, it is difficult to achieve a high breakdown voltage in a Schottky barrier diode using a nitride semiconductor.

Further, in order to suppress a decrease in breakdown voltage due to electric field concentration at the anode electrode end portion, a structure in which the anode electrode end portion is mesa-isolated by a trench in a Schottky barrier diode using gallium arsenide (GaAs) has been proposed ( Patent Document 1). However, the critical electric field of a wide band gap semiconductor such as gallium nitride (GaN) is high and close to the breakdown electric field of the insulating film. For this reason, high withstand voltage cannot be obtained only by mesa separation and filling the groove with an insulator.
JP 7-2111924 A

  An object of the present invention is to provide a semiconductor device including a Schottky barrier diode using a nitride semiconductor capable of obtaining a high breakdown voltage.

  A semiconductor device according to one embodiment of the present invention includes a first conductivity type nitride semiconductor substrate having an upper surface and a lower surface facing each other, and a first conductivity type first provided on the upper surface of the nitride semiconductor substrate. A nitride semiconductor region, a first main electrode provided on an upper surface of the first nitride semiconductor region and forming a Schottky junction with the first nitride semiconductor region, and the nitride semiconductor substrate A second main electrode that is electrically connected; and a trench that is selectively provided on a surface of the first nitride semiconductor region, the trench being buried by the first main electrode. It is characterized by that.

  According to the present invention, a semiconductor device including a Schottky barrier diode using a nitride semiconductor capable of obtaining a high breakdown voltage can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following embodiments, the first conductivity type is n-type and the second conductivity type is p-type. In addition, “n + type” described below indicates a semiconductor having a high n-type impurity concentration, and “n− type” indicates a semiconductor having a low n-type impurity concentration. Similarly, “p + type” and “p− type” indicate a semiconductor having a high p-type impurity concentration and a semiconductor having a low p-type impurity concentration, respectively.

(First embodiment)
(Configuration of Semiconductor Device According to First Embodiment)
FIG. 1 is a sectional view showing a structure of a semiconductor device according to the first embodiment of the present invention. FIG. 1 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. The semiconductor device of the present embodiment shown in FIG. 1 is a vertical Schottky barrier diode using a nitride semiconductor.

  As shown in FIG. 1, the semiconductor device according to the present embodiment has an upper surface and a lower surface facing each other, and is formed on an n + type semiconductor substrate 1 made of, for example, gallium nitride (GaN). On the upper surface of the n + type semiconductor substrate 1, for example, an n − type drift region 2 made of gallium nitride (GaN) is also provided. An anode electrode 3 is provided on the n − type drift region 2 so as to be electrically connected to the n − type drift region 2. A Schottky junction A is formed at the junction interface between the anode electrode 3 and the n − type drift region 2. A cathode electrode 4 is provided so as to be electrically connected to the lower surface of the n + type semiconductor substrate 1. The junction between the n + type semiconductor substrate 1 and the cathode electrode 4 is an ohmic junction. The anode electrode 3 is made of, for example, aluminum (Al), titanium (Ti), or the like, and the cathode electrode 4 is made of, for example, nickel (Ni).

  In the present embodiment, a plurality of trenches 5 are selectively formed on the surface of n − type drift region 2. An insulating film 6 is provided on the bottom and side walls of the trench 5, and the anode electrode 3 is embedded inside the trench 5 through the insulating film 6. Further, in the semiconductor device of the present embodiment, the insulating film 6 provided in the trench 5 is provided extending to the upper surface of the n − type drift region 2 toward the outer peripheral termination region from the trench 5. . The anode electrode 3 extends to the termination region outside the trench 5, and is provided on the n − type drift region 2 via the extended insulating film 6 on the outer periphery from the trench 5.

(Operation of the semiconductor device according to the first embodiment)
Next, the operation of the semiconductor device will be described. When a positive voltage is applied to the anode electrode 3 and a negative voltage is applied to the cathode electrode 4, free electrons in the n − -type drift region 2 can move to the anode electrode 3 side having a lower energy level. As a result, a current flows from the anode electrode 3 to the cathode electrode 4.

  On the other hand, when a negative voltage is applied to the anode electrode 3 and a positive voltage is applied to the cathode electrode 4, the free electrons of the anode electrode 3 cannot move to the n − type drift region 2 because of the Schottky barrier. As a result, no current flows from the cathode electrode 4 to the anode electrode 3. At this time, a depletion layer extends from the Schottky junction A between the anode electrode 3 and the n − type drift region 2, and a voltage is held in the n − type drift region 2. At this time, the depletion layer extending from the end of the Schottky junction A extends in both the horizontal direction horizontal to the n + type semiconductor substrate 1 and the vertical direction vertical to the semiconductor substrate 1. Therefore, a portion having a large curvature is generated in the depletion layer extending from the end portion of the Schottky junction A, and electric field concentration is likely to occur.

(Effect of the semiconductor device according to the first embodiment)
In the semiconductor device according to the present embodiment, trench 5 is formed in n − type drift region 2 outside the end of Schottky junction A between anode electrode 3 and n − type drift region 2. In addition, an anode electrode 3 is embedded in the trench 5 through an insulating film 6. Since the depletion layer extending from the Schottky junction A is curved along the trench 5, the electric field does not concentrate on the end portion of the anode electrode 3 that forms the Schottky junction A. Although the concentration of the electric field occurs at the bottom of the trench 5, no current flows to the anode electrode 3 embedded in the trench 5 because the insulating film 6 is provided on the bottom and side walls of the trench 5. Then, the voltage held in the n − type drift region 2 is shared by both the insulating film 6 and the n − type drift region 2, and a high breakdown voltage is obtained. In addition, since electric field concentration does not occur at the end of the anode electrode 3 in contact with the n − type drift region 2, it is possible to suppress reverse leakage current.

  In the semiconductor device according to the present embodiment, insulating film 6 is also provided on the surface of n − type drift region 2 in the termination region outside trench 5. The anode electrode 3 is extended to above the insulating film 6 outside the trench 5. The anode electrode 3 formed on the insulating film 6 acts as a field plate electrode, and the depletion layer curved along the trench 5 can be further extended in the lateral direction. Thereby, electric field concentration at the bottom of the trench 5 can be suppressed, and a high breakdown voltage semiconductor device can be realized.

(Modification of the semiconductor device according to the first embodiment)
Next, various modifications of the semiconductor device according to the first embodiment will be described with reference to FIGS.

  FIG. 2 is a cross-sectional view showing a structure of a first modification of the semiconductor device according to the first embodiment. FIG. 2 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 2, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 2, the trench 5 is formed not only in the vicinity of the end of the Schottky junction A formed by the anode electrode 3 and the n − type drift region 2 but also in the entire Schottky junction A in the element region. ing. An insulating film 6 is also provided in the trench 5 at the bottom and side walls, and the anode electrode 3 is embedded in the trench 5 through the insulating film 6.

  The semiconductor device shown in FIG. 2 can suppress the reverse electric field of the entire Schottky junction A formed by the n − type drift region 2 and the anode electrode 3. Thereby, the leakage current can be further reduced.

  FIG. 3 is a cross-sectional view showing a structure of a second modification of the semiconductor device according to the first embodiment. FIG. 3 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 3, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the semiconductor device shown in FIG. 3, the insulating film 6 does not reach the upper end B on the side where the Schottky junction A of the trench 5 is formed, and the n − type drift region 2 and the anode electrode 3 A Schottky junction A therebetween extends to the upper end B of the sidewall of the trench 5.

  The semiconductor device shown in FIG. 3 can increase the contact area between the anode electrode 3 and the n − -type drift region 2, and can reduce the on-resistance.

  FIG. 4 is a cross-sectional view showing a structure of a third modification of the semiconductor device according to the first embodiment. FIG. 4 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 4, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 4, an insulating film 7 is formed on the insulating film 6 in the termination region on the outer periphery from the trench 5. In other words, the insulating films 6 and 7 are formed so that the total thickness of the insulating films 6 and 7 becomes thicker from the trench 5 toward the outer periphery. The anode electrode 3 is provided on the n − type drift region 2 via the insulating films 6 and 7 on the outer periphery of the trench 5.

  The semiconductor device shown in FIG. 4 is formed so that the total thickness of the insulating films 6 and 7 is thicker than the thickness at the inner periphery of the trench 5 in the termination region at the outer periphery of the trench 5. In the vicinity of the end of the anode electrode 3 acting as a Thereby, concentration of the electric field at the bottom of the trench 5 and the end of the anode electrode 3 can be suppressed.

  FIG. 5 is a sectional view showing a structure of a fourth modification of the semiconductor device according to the first embodiment. FIG. 5 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 5, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 5, the insulating film 6 extends to the surface of the n − type drift region 2 in the termination region. An n-type field stop region 8 is provided at the end of the termination region, and a field stop electrode 9 is connected to the field stop region 8.

  Since the Schottky barrier diode is processed from a wafer to a chip by dicing, the side surface of the diced chip is damaged. When a voltage is applied to the damaged chip side surface, a leakage current may flow. There is also a problem that a stable breakdown voltage cannot be obtained. In the semiconductor device shown in FIG. 5, since the field stop electrode 9 and the field stop region 8 are provided, the depletion layer extending from the Schottky junction A can be prevented from reaching the chip side surface, and the voltage is applied to the side surface of the chip. Is not applied.

  FIG. 6 is a cross-sectional view showing a structure of a fifth modification of the semiconductor device according to the first embodiment. FIG. 6 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 6, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 6, a field stop electrode trench 10 is formed on the surface of the n − type drift region 2 in the termination region. The insulating film 6 provided extending to the termination region is also provided on the bottom and side walls of the field stop electrode trench 10. The inside of the field stop electrode trench 10 is buried with a field stop electrode 9 through an insulating film 6.

  In the semiconductor device shown in FIG. 6, since the field stop electrode trench 10 is formed, the depletion layer extending from the Schottky junction A between the n − type drift region 2 and the anode electrode 3 reaches the chip side surface. Can be prevented more reliably. Since the field stop electrode trench 10 can be formed at the same time as the trench 5, it is not necessary to provide the n-type field stop region 8, so that the semiconductor device can be formed with fewer steps.

(Second Embodiment)
(Configuration of Semiconductor Device According to Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a cross-sectional view showing the structure of the semiconductor device according to the second embodiment of the present invention. FIG. 7 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 7, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, a p-type guard ring region 11 is provided on the upper surface of the n − -type drift region 2 forming the Schottky junction A with the anode electrode 3 so as to be in contact with the anode electrode 3. Guard ring region 11 is provided in contact with the sidewall of trench 5 in the vicinity of the end of Schottky junction A formed by anode electrode 3 and n − type drift region 2. The guard ring region 11 is provided, for example, by doping the n − type drift region 2 with fluorine (F), chlorine (Cl), magnesium (Mg), manganese (Mn), or the like.

(Effect of the semiconductor device according to the second embodiment)
When a reverse voltage (a negative voltage is applied to the anode electrode and a positive voltage is applied to the cathode electrode) is applied to the Schottky barrier diode, the generated holes accumulate in the vicinity of the Schottky junction A and Increase the electric field. This electric field promotes the generation of electron-hole pairs due to avalanche breakdown, so that the avalanche current continues to increase and the device is destroyed.

  In the semiconductor device according to the present embodiment, by forming guard ring region 11, holes generated in n − type drift region 2 due to avalanche breakdown can be quickly discharged. Therefore, it is possible to prevent the element from being destroyed by the avalanche breakdown.

  Further, even when an avalanche breakdown occurs, a current can flow stably, and the reverse voltage applied to the semiconductor device is clamped by the avalanche breakdown voltage and does not increase. Thereby, the voltage applied to the surrounding elements connected to the Schottky barrier diode does not increase, and the destruction of the surrounding elements can be prevented.

(Modification of Semiconductor Device According to Second Embodiment)
Next, a modification of the semiconductor device according to the second embodiment will be described with reference to FIG.

  FIG. 8 is a cross-sectional view showing the structure of a modification of the semiconductor device according to the second embodiment. FIG. 8 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 8, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. The semiconductor device shown in FIG. 8 includes a plurality of p-type guard ring regions not only in the vicinity of the end portion of the Schottky junction A formed by the anode electrode 3 and the n − type drift region 2 but also in the entire Schottky junction A. 11 is provided.

  When a reverse voltage (a negative voltage is applied to the anode electrode and a positive voltage is applied to the cathode electrode) is applied to the Schottky barrier diode, the electric field applied to the Schottky junction A increases, so that the Schottky barrier is caused by the tunneling effect. The passing current will increase. In the semiconductor device shown in FIG. 8, by forming the plurality of guard ring regions 11, the electric field applied to the Schottky junction A is relaxed, and the leakage current flowing through the Schottky junction A can be reduced. Further, by increasing the surface area of the guard ring region 11 formed in the n − type drift region 2, the hole discharge is promoted when a reverse voltage is applied, and a higher avalanche resistance can be obtained.

(Third embodiment)
(Configuration of Semiconductor Device According to Third Embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 9 is a sectional view showing the structure of a semiconductor device according to the third embodiment of the present invention. FIG. 9 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 9, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the present embodiment, the anode electrode is composed of two different types of metals, the anode electrode 3 and the anode electrode 12. The anode electrode 3 is provided so that a Schottky junction A is formed at the junction interface with the n − type drift region 2. The anode electrode 3 is made of a metal having a large Schottky barrier height, such as nickel (Ni) or platinum (Pt). A plurality of anode electrodes 12 are provided on the n − -type drift region 2 and are covered with the anode electrode 3. The anode electrode 12 forms a Schottky junction C with the n − type drift layer 2. The anode electrode 12 is made of a metal having a small Schottky barrier height, such as aluminum (Al) or titanium (Ti).

(Effect of the semiconductor device according to the third embodiment)
In the semiconductor device according to the present embodiment, even when a reverse voltage (a negative voltage is applied to the anode electrode and a positive voltage is applied to the cathode electrode) is applied to the semiconductor device, the anode electrode 3 having a large Schottky barrier height is used. , Leakage current can be reduced. When a forward voltage (a positive voltage is applied to the anode electrode and a negative voltage is applied to the cathode electrode) is applied to the semiconductor device, a forward current is passed through the anode electrode 12 having a small Schottky barrier height. As a result, a low on-resistance can be realized.

(Fourth embodiment)
(Configuration of Semiconductor Device According to Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a sectional view showing the structure of a semiconductor device according to the fourth embodiment of the present invention. FIG. 10 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device according to the present embodiment shown in FIG. 10, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, a semiconductor layer 13 made of aluminum gallium nitride (AlGaN) is provided on the upper surface of an n − type drift region 2 formed on an n + type semiconductor substrate 1 made of gallium nitride (GaN). AlGaN is a nitride semiconductor having a larger band gap than GaN. A heterojunction D is formed at the junction interface between the n − type drift region 2 and the AlGaN layer 13. On the AlGaN layer 13, an anode electrode 3 is provided so as to be electrically connected to the n − type drift region 2 through the AlGaN layer 13. A Schottky junction E is formed at the junction interface between the anode electrode 3 and the AlGaN layer 13. In the present embodiment, a plurality of trenches 5 are selectively formed on the surface of the AlGaN layer 13 so as to penetrate the AlGaN layer 13 and reach the n − type drift region 2. An insulating film 6 is provided on the bottom and side walls of the trench 5, and the anode electrode 3 is embedded inside the trench 5 through the insulating film 6.

(Effect of the semiconductor device according to the fourth embodiment)
Since AlGaN has a larger band gap than GaN, the height of the barrier of the Schottky junction E formed at the junction interface between the AlGaN layer 13 and the anode electrode 3 is increased. Thereby, it is possible to reduce the leakage current when the reverse voltage is applied. The height of the barrier of the Schottky junction E is uniquely determined by the metal constituting the anode electrode 3, but it is possible to control the height of the Schottky barrier by inserting the AlGaN layer 13. Become. Specifically, the Schottky barrier height can be changed by changing the Al composition ratio of Al _x Ga _1-x N (0 <x ≦ 1) constituting the AlGaN layer 13.

(Modification of Semiconductor Device According to Fourth Embodiment)
Next, a modification of the semiconductor device according to the fourth embodiment will be described with reference to FIG.

  FIG. 11 is a cross-sectional view showing a structure of a modification of the semiconductor device according to the fourth embodiment. FIG. 11 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 11, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 11, the anode electrode is provided by two different types of metals, the anode electrode 3 and the anode electrode 12. The anode electrode 3 is provided so that a Schottky junction E is formed at the junction interface with the AlGaN layer 13. The anode electrode 3 is made of a metal having a large Schottky barrier height, such as nickel (Ni) or platinum (Pt). A plurality of anode electrodes 12 are provided on the AlGaN layer 13 and are covered with the anode electrode 3. The anode electrode 12 forms a Schottky junction C with the AlGaN layer 13. The anode electrode 12 is made of a metal having a small Schottky barrier height, such as aluminum (Al) or titanium (Ti).

  In the present embodiment, when the height of the Schottky barrier is increased by providing the AlGaN layer 13, a current starts to flow when a forward voltage (a positive voltage is applied to the anode electrode and a negative voltage is applied to the cathode electrode) is applied. The voltage (rising voltage) becomes large. In the semiconductor device shown in FIG. 11, since the anode electrodes 3 and 12 are formed using two kinds of metals, the rising voltage can be reduced and the reverse leakage current can also be reduced. In order to reduce the reverse leakage current, the AlGaN layer 13 is preferably undoped.

(Fifth embodiment)
(Configuration of Semiconductor Device According to Fifth Embodiment)
Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 12 is a sectional view showing the structure of a semiconductor device according to the fifth embodiment of the present invention. FIG. 12 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 12, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, a semiconductor layer 14 made of indium gallium nitride (InGaN) is selectively provided on the upper surface of the n − type drift region 2 formed on the n + type semiconductor substrate 1 made of gallium nitride (GaN). ing. InGaN is a nitride semiconductor having a smaller band gap than GaN. A heterojunction D is formed at the junction interface between the n − type drift region 2 and the InGaN layer 14. An anode electrode 3 is provided on the InGaN layer 14 so as to be electrically connected to the n − type drift region 2 via the InGaN layer 14. A Schottky junction E is formed at the junction interface between the anode electrode 3 and the InGaN layer 14.

(Effect of the semiconductor device according to the fifth embodiment)
Due to process variations after the anode electrode 3 is formed, the Schottky barrier height of the Schottky junction E between the anode electrode 3 and the InGaN layer 14 is likely to vary. In the semiconductor device according to the present embodiment, by using the InGaN layer 14 having a small band gap, the Schottky barrier height of the Schottky junction E between the anode electrode 3 and the InGaN layer 14 is reduced, and the n − type is obtained. The heterojunction D between the drift region 2 and the InGaN layer 14 is used as a barrier. Since the InGaN layer 14 can be formed by crystal growth, the barrier height of the heterojunction D formed at the junction interface between the InGaN layer 14 and the n − type drift region 2 can be stabilized.

  Here, in order to obtain a high avalanche resistance, the InGaN layer 14 is desirably p-type. Since the barrier due to the heterojunction D exists in both the conduction band and the valence band, hole injection does not occur even when a voltage is applied in the forward direction. For this reason, even if the n − type drift region 2 and the InGaN layer 14 are pn junction diodes, a unipolar operation similar to that of a Schottky barrier diode is achieved and high-speed operation can be expected. At this time, in order to realize a low ohmic resistance between the anode electrode 3 and the p-type InGaN layer 14, it is desirable to use platinum (Pt) or the like for the anode electrode 3.

(Modification of Semiconductor Device According to Fifth Embodiment)
Next, a modification of the semiconductor device according to the fifth embodiment will be described with reference to FIG.

  FIG. 13 is a cross-sectional view showing the structure of a modification of the semiconductor device according to the fifth embodiment. FIG. 13 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 13, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 13, a semiconductor layer 15 made of polysilicon (p-Si) is selectively formed on the upper surface of an n − type drift region 2 formed on an n + type semiconductor substrate 1 made of gallium nitride (GaN). Is provided. Polysilicon is a semiconductor having a smaller band gap than GaN. A heterojunction D is formed at the junction interface between n − type drift region 2 and polysilicon layer 15. An anode electrode 3 is provided on the polysilicon layer 15 so as to be electrically connected to the n − type drift region 2 through the polysilicon layer 15. A Schottky junction E is formed at the junction interface between the anode electrode 3 and the polysilicon layer 15.

  If the semiconductor material has a band gap as narrow as that of silicon, the barrier height of the heterojunction D of about 1 eV can be obtained even if not a single crystal. In the semiconductor device shown in FIG. 13, leakage current can be reduced by using polysilicon which does not require crystal growth. Further, the polysilicon layer 15 can obtain an ohmic resistance lower than that of the InGaN layer 14.

(Sixth embodiment)
(Configuration of Semiconductor Device According to Sixth Embodiment)
Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 14 is a sectional view showing a structure of a semiconductor device according to the sixth embodiment of the present invention. FIG. 14 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 14, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the present embodiment, a plurality of trenches 5 are selectively formed on the surface of n − type drift region 2. An insulating film 6 is provided on the side wall of the trench 5, and the anode electrode 3 is embedded inside the trench 5 through the insulating film 6. A p-type guard ring region 16 made of a nitride semiconductor is provided in the n − type drift region 2 made of a nitride semiconductor so as to be in contact with the bottom of the trench 5. The insulating film 6 provided in the trench 5 is provided extending on the upper surface of the n − type drift region 2 toward the outer peripheral termination region from the trench 5. The anode electrode 3 extends to the termination region outside the trench 5, and is provided on the n − type drift region 2 via the extended insulating film 6 on the outer periphery from the trench 5.

(Effect of the semiconductor device according to the sixth embodiment)
In the semiconductor device according to the present embodiment, since guard ring region 16 is connected to anode electrode 3, pn junction diode is formed by guard ring region 16 and n − type drift region 2. Here, since the guard ring region 16 is closer to the n + type semiconductor substrate 1 than the junction interface of the Schottky junction A, the breakdown voltage of the semiconductor device is determined by the breakdown voltage of the pn junction diode. Even if the Schottky barrier height varies due to process variations after the anode electrode 3 is formed, a stable breakdown voltage can be obtained.

  An avalanche breakdown that occurs when a high voltage is applied occurs at the pn junction between the guard ring region 16 and the n − type drift region 2. Therefore, holes generated by avalanche breakdown are quickly discharged from the guard ring region 16, and a high avalanche resistance can be obtained.

(Modification of Semiconductor Device According to Sixth Embodiment)
Next, various modifications of the semiconductor device according to the sixth embodiment will be described with reference to FIGS.

  FIG. 15 is a cross-sectional view showing a structure of a first modification of the semiconductor device according to the sixth embodiment. FIG. 15 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 15, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 15, the trench 5 is formed not only in the vicinity of the end of the Schottky junction A formed by the anode electrode 3 and the n − -type drift region 2 but also in the entire Schottky junction A. Also in the trench 5, an insulating film 6 is provided on the side wall, and the anode electrode 3 is embedded in the trench 5 through the insulating film 6. A p-type guard ring region 16 is provided in the n − -type drift region 2 so as to be in contact with the bottoms of the plurality of trenches 5.

  The semiconductor device shown in FIG. 15 can suppress the reverse electric field of the entire Schottky junction A formed by the n − type drift region 2 and the anode electrode 3. Thereby, the leakage current can be further reduced. Further, since the guard ring region 16 connected to the anode electrode 3 is increased, the resistance of hole discharge at the time of avalanche breakdown is lowered, and higher avalanche resistance can be obtained.

  FIG. 16 is a cross-sectional view showing a structure of a second modification of the semiconductor device according to the sixth embodiment. FIG. 16 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 16, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 16, a p-type guard ring region 16 is provided in the n − -type drift region 2 so as to be in contact with the bottom and side walls of the trench 5. The insulating film 6 is provided on the upper surface of the n − -type drift region 2 from the upper end portion of the trench 5 toward the outer peripheral termination region from the trench 5. The anode electrode 3 extends to the termination region outside the trench 5, and is provided on the n − type drift region 2 via the insulating film 6 on the outer periphery from the trench 5.

  In the semiconductor device shown in FIG. 16, no insulating film is provided on the side wall and bottom of the trench 5, and the guard ring region 16 and the anode electrode 3 are in contact with each other. Since the p-type guard ring region 16 is provided on the side wall and bottom of the trench 5, the reverse leakage current does not increase. By forming in this way, the Schottky junction area is increased, and the forward voltage when turned on can be lowered.

  FIG. 17 is a cross-sectional view showing a structure of a third modification of the semiconductor device according to the sixth embodiment. FIG. 17 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 17, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 17, a p-type guard ring region 16 is formed over the entire Schottky junction A formed by the anode electrode 3 and the n − -type drift region 2.

  The semiconductor device illustrated in FIG. 17 can suppress the entire reverse electric field of the Schottky junction A. Thereby, the leakage current can be further reduced. When the guard ring region 16 is formed, it can be formed simultaneously with the guard ring region 16 at the bottom of the trench and the guard ring region 16 below the Schottky junction A. Thus, the semiconductor device shown in FIG. 17 can be formed without increasing the number of steps.

(Seventh embodiment)
(Configuration of Semiconductor Device According to Seventh Embodiment)
Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 18 is a cross-sectional view showing the structure of the semiconductor device according to the seventh embodiment of the present invention. FIG. 18 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 18, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, an insulating film 17 is provided on the upper surface of the n − type drift region 2. A plurality of trenches 5 are selectively provided so as to penetrate the insulating film 17 and reach the n − type drift region 2. An insulating film 6 is provided on the side wall of the trench 5. The insulating film 17 and the insulating film 6 are provided on the upper surface of the n − -type drift region 2 so as to extend from the trench 5 toward the outer peripheral termination region. Further, the insulating film 17 and the insulating film 6 are partially removed on the n − type drift region 2, and an opening F through which the n − type drift region 2 is exposed is provided.

  A p-type polysilicon layer 18 is provided on the upper surface of the n − -type drift region 2 provided with the insulating film 17 and the insulating film 6. The polysilicon layer 18 is uniformly provided on the insulating film 17 and the insulating film 6, on the side walls and bottom of the trench 5, and on the opening F.

  An anode electrode 3 is provided on the polysilicon layer 18. The anode electrode 3 is electrically connected to the n − type drift region 2 through the polysilicon layer 18 in the opening F. A Schottky junction G is formed at the junction interface between the anode electrode 3 and the polysilicon layer 18. Further, the anode electrode 3 is embedded in the trench 5 through the polysilicon layer 18 and the insulating film 6.

(Effect of the semiconductor device according to the seventh embodiment)
In the present embodiment, a heterojunction H is formed at the junction interface between n − type drift region 2 and polysilicon layer 18. By using this polysilicon layer 18, leakage current can be reduced.

  A pn junction diode is formed by polysilicon layer 18 and n − type drift region 2 at the bottom of trench 5. Here, since the pn junction diode between the polysilicon layer 18 and the n − type drift region 2 is closer to the n + type semiconductor substrate 1 than the interface of the heterojunction H, the avalanche breakdown at the time of applying a high voltage is a trench. Occurs at the bottom of 5. In addition to increasing the radius of curvature of the depletion layer by the trench 5, it is possible to realize a stable high breakdown voltage by limiting the avalanche breakdown location.

(Modification of Semiconductor Device According to Seventh Embodiment)
Next, a modification of the semiconductor device according to the seventh embodiment will be described with reference to FIG.

  FIG. 19 is a cross-sectional view showing a structure of a modification of the semiconductor device according to the seventh embodiment. FIG. 19 shows an element region in which a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 19, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 19, a plurality of trenches 5 are selectively provided on the surface of the n − type drift region 2. A p-type polysilicon layer 18 is provided on the upper surface of the n − -type drift region 2 including the bottom and side walls of the trench 5. An insulating film 6 is provided on the entire surface of the n − type drift region 2 including on the polysilicon layer 18. The insulating film 6 is provided extending on the n − type drift region 2 from the trench toward the outer peripheral termination region. In addition, the insulating film 6 is partially removed on the n − type drift region 2, and an opening F through which the polysilicon layer 18 is exposed is provided.

  An anode electrode 3 is provided on the insulating film 6. The anode electrode 3 is electrically connected to the n − type drift region 2 through the polysilicon layer 18 in the opening F. A Schottky junction G is formed at the junction interface between the anode electrode 3 and the polysilicon layer 18. In addition, the anode electrode 3 is embedded in the trench 5 through the p-type polysilicon layer 18 and the insulating film 6.

  With this configuration, the same effect as that of the semiconductor device shown in FIG. 18 can be obtained.

(Eighth embodiment)
(Configuration of Semiconductor Device According to Eighth Embodiment)
Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 20 is a sectional view showing the structure of a semiconductor device according to the eighth embodiment of the present invention. FIG. 20 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device according to the present embodiment shown in FIG. 20, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the present embodiment, the insulating film 6 provided on the side wall and bottom of the trench 5 is provided on the n − type drift region 2 so as to extend from the trench 5 toward the outer peripheral termination region. A guard ring electrode 19 having a floating potential is provided around the anode electrode 3 extending from the trench 5 to the outer peripheral termination region. The guard ring electrode 19 is provided on the n − type drift region 2 via the insulating film 6.

(Effect of the semiconductor device according to the eighth embodiment)
In the present embodiment, by forming the guard ring electrode 19, the depletion layer extending from the Schottky junction A is extended from the bottom of the trench 5 to the lower part of the guard ring electrode 19. Concentration of the electric field at the end of the anode electrode 3 extending from the trench 5 to the outer peripheral termination region is suppressed, and a high breakdown voltage semiconductor device can be realized.

(Modification of Semiconductor Device According to Eighth Embodiment)
Next, various modifications of the semiconductor device according to the eighth embodiment will be described with reference to FIGS.

  FIG. 21 is a cross-sectional view showing a structure of a first modification of the semiconductor device according to the eighth embodiment. FIG. 21 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 21, portions having the same configuration as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 21, a guard ring electrode trench 20 is provided on the surface of the n − type drift region 2 below the guard ring electrode 19. The insulating film 6 provided extending to the lower part of the guard ring electrode 19 is also provided on the bottom and side walls of the guard ring electrode trench 20. A guard ring electrode 19 is embedded inside the guard ring electrode trench 20 via the insulating film 6.

  In the semiconductor device shown in FIG. 21, a guard ring electrode trench 20 is formed below the guard ring electrode 19. The depletion layer extending from the Schottky junction A has a large radius of curvature below the guard ring electrode 19. The concentration of the electric field at the end of the guard ring electrode 19 is alleviated, and a higher breakdown voltage semiconductor device can be realized.

  FIG. 22 is a cross-sectional view showing a structure of a second modification of the semiconductor device according to the eighth embodiment. FIG. 22 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 22, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 22, an insulating film 21 is provided on the upper surface of the n − -type drift region 2 in the termination region and the element region. In the element region, a plurality of trenches 5 are selectively provided so as to penetrate the insulating film 21 and reach the n − type drift region 2. An insulating film 6 is provided on the side wall and bottom of the trench 5. The insulating film 21 and the insulating film 6 are provided on the upper surface of the n − type drift region 2 so as to extend from the trench 5 toward the outer peripheral termination region. Further, the insulating film 21 and the insulating film 6 are partially removed on the n − type drift region 2, and an opening F through which the n − type drift region 2 is exposed is provided.

  An anode electrode 3 is provided on the insulating film 21 and the insulating film 6. The anode electrode 3 is electrically connected to the n − type drift region 2 in the opening F. A Schottky junction A is formed at the junction interface between the anode electrode 3 and the n − type drift region 2. Further, the anode electrode 3 is embedded in the trench 5 through the insulating film 6.

  In the semiconductor device shown in FIG. 22, a guard ring electrode 19 having a floating potential is provided around the anode electrode 3 that extends from the trench 5 to the outer peripheral termination region. A guard ring electrode trench 20 is provided below the guard ring electrode 19 so as to penetrate the insulating film 21 and reach the n − type drift region 2. The insulating film 6 provided extending to the lower part of the guard ring electrode 19 is also provided on the bottom and side walls of the guard ring electrode trench 20. A guard ring electrode 19 is embedded inside the guard ring electrode trench 20 via the insulating film 6.

  In the semiconductor device shown in FIG. 22, by adjusting the thicknesses of the insulating films 21 and 6, the field plate effect at the end of the anode electrode 3 and the end of the guard ring electrode 19 can be modulated. Can be obtained.

  FIG. 23 is a cross-sectional view showing the structure of the third modification of the semiconductor device according to the eighth embodiment. FIG. 23 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element region. In the semiconductor device shown in FIG. 23, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 23, the insulating film 6 is provided on the sidewall of the trench 5. A p-type guard ring region 22 is provided in the n − -type drift region 2 so as to be in contact with the bottom of the trench 5. The insulating film 6 provided in the trench 5 is provided extending on the n − type drift region 2 toward the outer peripheral termination region from the trench 5. A guard ring electrode 19 having a floating potential is provided around the anode electrode 3 extending from the trench 5 to the outer peripheral termination region. The guard ring electrode 19 is provided on the n − type drift region 2 via the insulating film 6.

  A guard ring electrode trench 20 is provided on the surface of the n − type drift region 2 below the guard ring electrode 19. The insulating film 6 provided extending to the lower part of the guard ring electrode 19 is also provided on the side wall of the guard ring electrode trench 20. A guard ring electrode 19 is buried inside the guard ring electrode trench 20 via the insulating film 6. A p-type guard ring region 22 is provided in the n − -type drift region 2 so as to be in contact with the bottom of the guard ring electrode trench 20.

  In the semiconductor device shown in FIG. 23, a pn junction diode is formed at the bottom of the trench 5 and the bottom of the guard ring electrode trench 20. Thereby, a stable pressure resistance and a high avalanche resistance can be obtained.

  FIG. 24 is a cross-sectional view showing the structure of the fourth modification example of the semiconductor device according to the eighth embodiment. FIG. 24 shows an element region where a semiconductor element such as a Schottky barrier diode is formed and a termination region surrounding the element area. In the semiconductor device shown in FIG. 24, portions having the same configurations as those of the semiconductor device according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the semiconductor device shown in FIG. 24, the trench 5 is formed not only in the vicinity of the end of the Schottky junction A formed by the anode electrode 3 and the n − type drift region 2 but also in the entire Schottky junction A. Also in the trench 5, an insulating film 6 is provided on the side wall, and the anode electrode 3 is embedded in the trench 5 through the insulating film 6. A p-type guard ring region 22 is provided in the n − -type drift region 2 so as to be in contact with the bottoms of the plurality of trenches 5.

  The semiconductor device shown in FIG. 24 can suppress the reverse electric field of the entire Schottky junction A formed by the n − type drift region 2 and the anode electrode. Thereby, the reverse leakage current can be further reduced.

  In the semiconductor device shown in FIGS. 20 to 24, the structure in which one guard ring electrode 19 is formed on the outer periphery of the anode electrode 3 is shown. However, another guard ring electrode is formed on the outer periphery of the guard ring electrode 19. It is also possible to form Further, it is possible to provide a guard ring region also below another guard ring electrode formed on the outer periphery.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change, addition, a combination, etc. are possible within the range which does not deviate from the meaning of invention. For example, in the embodiment, the Schottky barrier diode using gallium nitride as the material of the nitride semiconductor has been described. As the nitride semiconductor, for example, aluminum gallium nitride (AlGaN), aluminum nitride (AlN), indium gallium nitride ( Various nitride semiconductors such as InGaN), indium nitride (InN), indium aluminum gallium nitride (InAlGaN), or boron nitride (BN) can be used.

  In the fourth and fifth embodiments, the combination of nitride semiconductors has been described as a combination of AlGaN / GaN or InGaN / GaN, but GaN / InGaN, AlN / AlGaN, BAlN / GaN, GaN. It is also possible to implement various combinations of nitride semiconductors such as / AlGaN or AlGaN / AlN.

  Embodiments of the semiconductor device according to the present invention include the following.

(1) (FIGS. 1 to 24)
A first conductivity type nitride semiconductor substrate having an upper surface and a lower surface facing each other;
A first conductivity type first nitride semiconductor region provided on an upper surface of the nitride semiconductor substrate;
A first main electrode provided on an upper surface of the first nitride semiconductor region and forming a Schottky junction with the first nitride semiconductor region;
A second main electrode electrically connected to the nitride semiconductor substrate;
A trench selectively provided on the surface of the first nitride semiconductor region,
The semiconductor device according to claim 1, wherein the trench is filled with the first main electrode.

(2) (FIGS. 1-13)
A first insulating film provided on the sidewall and bottom of the trench and on the upper surface of the first nitride semiconductor region on the outer periphery of the trench;
The trench is filled with the first main electrode through the first insulating film;
The semiconductor device according to (1), wherein the first main electrode is provided on an upper surface of the first nitride semiconductor region via the first insulating film at an outer periphery from the trench.

(3) (Figure 2)
The semiconductor device according to (2), wherein a plurality of the trenches are provided.

(4) (Fig. 4)
The semiconductor device according to (2), wherein the first insulating film is provided so as to become thicker toward the outside at the outer periphery than the trench.

(5) (Figure 5)
An element region on the nitride semiconductor substrate; and a termination region provided so as to surround the element region;
(2) The semiconductor device according to (2), wherein a field stop electrode connected to the first nitride semiconductor region is provided in the termination region.

(6) (Fig. 6)
A field stop electrode trench provided on the surface of the first nitride semiconductor region of the termination region;
The semiconductor device according to (5), wherein the field stop electrode trench is filled with the field stop electrode.

(7) (Figure 7)
The semiconductor according to (2), further comprising: a first guard ring region of a second conductivity type provided on an upper surface of the first nitride semiconductor region so as to be in contact with the first main electrode. apparatus.

(8) (Figure 8)
The semiconductor device according to (7), wherein a plurality of the first guard ring regions are provided.

(9) (Figure 9)
The semiconductor device according to (2), wherein the first main electrode is made of two kinds of metals.

(10) (FIGS. 10-13)
A second semiconductor region provided on an upper surface of the first nitride semiconductor region and having a band gap different from that of the first nitride semiconductor region forming a Schottky junction with the first main electrode; (2) The semiconductor device according to (2).

(11) (FIGS. 10 to 11)
The semiconductor device according to (10), wherein the second semiconductor region is made of a semiconductor material having a band gap larger than that of the first semiconductor region.

(12) (FIGS. 10 to 11)
The semiconductor device according to (11), wherein the second semiconductor region is made of a nitride semiconductor.

(13) (FIGS. 12 to 13)
The semiconductor device according to (10), wherein the second semiconductor region is made of a semiconductor material having a band gap smaller than that of the first semiconductor region.

(14) (Fig. 12)
The semiconductor device according to (13), wherein the second semiconductor region is made of a nitride semiconductor.

(15) (FIGS. 14 to 19)
(2) The semiconductor device according to (1), further comprising a third nitride semiconductor region of a second conductivity type provided in the first nitride semiconductor region so as to be in contact with the bottom of the trench.

(16) (Fig. 16)
The semiconductor device according to (15), wherein the third nitride semiconductor region is provided in contact with a sidewall of the trench.

(17) (FIGS. 20 to 24)
The semiconductor device according to (1), further comprising a guard ring electrode provided on the first insulating film at an outer periphery from the trench.

(18) (FIGS. 21-24)
A guard ring electrode trench selectively provided on a surface of the first nitride semiconductor region;
The semiconductor device according to (17), wherein the guard ring electrode trench is filled with the guard ring electrode.

(19) (FIGS. 23 to 24)
(2) The semiconductor according to (18), further comprising a second conductivity type second guard ring region provided in the first nitride semiconductor region so as to be in contact with the bottom of the guard ring electrode trench. apparatus.

It is sectional drawing which shows the structure of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the 1st modification of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the 2nd modification of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the 3rd modification of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the 4th modification of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the 5th modification of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 2nd Embodiment. It is sectional drawing which shows the structure of the modification of the semiconductor device which concerns on 2nd Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 4th Embodiment. It is sectional drawing which shows the structure of the modification of the semiconductor device which concerns on 4th Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 5th Embodiment. It is sectional drawing which shows the structure of the modification of the semiconductor device which concerns on 5th Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 6th Embodiment. It is sectional drawing which shows the structure of the 1st modification of the semiconductor device which concerns on 6th Embodiment. It is sectional drawing which shows the structure of the 2nd modification of the semiconductor device which concerns on 6th Embodiment. It is sectional drawing which shows the structure of the 3rd modification of the semiconductor device which concerns on 6th Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 7th Embodiment. It is sectional drawing which shows the structure of the modification of the semiconductor device which concerns on 7th Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 8th Embodiment. It is sectional drawing which shows the structure of the 1st modification of the semiconductor device which concerns on 8th Embodiment. It is sectional drawing which shows the structure of the 2nd modification of the semiconductor device which concerns on 8th Embodiment. It is sectional drawing which shows the structure of the 3rd modification of the semiconductor device which concerns on 8th Embodiment. It is sectional drawing which shows the structure of the 4th modification of the semiconductor device which concerns on 8th Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... n + type semiconductor substrate, 2 ... n- type drift region, 3 ... Anode electrode, 4 ... Cathode electrode, 5 ... Trench, 6, 7 ... Insulating film, ..Field stop region, 9 ... Field stop electrode, 10 ... Trench for field stop electrode, 11 ... Guard ring region, 12 ... Anode electrode, 13 ... AlGaN layer, 14 ... InGaN layer, 15 ... polysilicon layer, 16 ... guard ring region, 17 ... insulating film, 18 ... polysilicon layer, 19 ... guard ring electrode, 20 ... for guard ring electrode Trench, 21 ... insulating film, 22 ... guard ring region.

Claims (5)

A first conductivity type nitride semiconductor substrate having an upper surface and a lower surface facing each other;
A first conductivity type first nitride semiconductor region provided on an upper surface of the nitride semiconductor substrate;
A first main electrode provided on an upper surface of the first nitride semiconductor region and forming a Schottky junction with the first nitride semiconductor region;
A second main electrode electrically connected to the nitride semiconductor substrate;
A trench selectively provided on the surface of the first nitride semiconductor region,
The semiconductor device according to claim 1, wherein the trench is filled with the first main electrode. A first insulating film provided on the sidewall and bottom of the trench and on the upper surface of the first nitride semiconductor region on the outer periphery of the trench;
The trench is filled with the first main electrode through the first insulating film;
The semiconductor device according to claim 1, wherein the first main electrode is provided on an upper surface of the first nitride semiconductor region via the first insulating film at an outer periphery from the trench. .   2. The semiconductor device according to claim 1, further comprising: a second conductivity type second nitride semiconductor region provided in the first nitride semiconductor region so as to be in contact with a bottom portion of the trench.   4. The semiconductor device according to claim 1, further comprising a guard ring electrode provided on the first insulating film on an outer periphery of the trench. 5. A guard ring electrode trench selectively provided on a surface of the first nitride semiconductor region;
5. The semiconductor device according to claim 4, wherein the guard ring electrode trench is filled with the guard ring electrode.

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