Schottky barrier diode

Abstract

The technical problem of the present invention is to alleviate an electric field generated in a drift layer when a reverse voltage is applied in a Schottky barrier diode using gallium oxide. A Schottky barrier diode (1) is provided with: a semiconductor substrate (20) comprising gallium oxide and a drift layer (30); and an anode electrode (40) and a cathode electrode (50). The drift layer (30) has an outer peripheral trench (32) surrounding the anode electrode (40) in plan view. The outer peripheral groove (32) includes an inner peripheral wall (33), an outer peripheral wall (34), a bottom surface (35), an inner peripheral corner portion (36), and an outer peripheral corner portion (37). The inner peripheral wall (33) and the inner peripheral corner section (36) are covered by the anode electrode (40) via an insulating film (60), and the outer peripheral corner section (37) is covered by a semiconductor material (70) of the opposite conductivity type to the drift layer (30). As a result, when a reverse voltage is applied, an electric field generated around the inner peripheral corner section (36) in the drift layer (30) can be mitigated.

Description

Technical Field

[0001] The present invention relates to a Schottky barrier diode, and in particular to a Schottky barrier diode using gallium oxide. Background Art

[0002] A Schottky barrier diode is a rectifying element that utilizes a Schottky barrier generated by the junction of a metal and a semiconductor, and has the characteristics of lower forward voltage and faster switching speed than a normal diode having a PN junction. Therefore, a Schottky barrier diode is sometimes used as a switching element for a power device.

[0003] When using Schottky barrier diodes as switching elements for power devices, it is necessary to ensure sufficient reverse withstand voltage. Therefore, sometimes silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), etc. with a larger band gap are used instead of silicon (Si). Among them, the band gap of gallium oxide is 4.8 to 4.9 eV, which is very large, and the dielectric breakdown electric field is also about 8 MV / cm, which is very large. Therefore, Schottky barrier diodes using gallium oxide are very promising as switching elements for power devices. Examples of Schottky barrier diodes using gallium oxide are recorded in Patent Document 1.

[0004] The Schottky barrier diode described in Patent Document 1 has the following structure: a drift layer formed of gallium oxide is provided with an outer peripheral groove surrounding the anode electrode in a plan view, and the outer peripheral groove is buried with a semiconductor material of a conductivity type opposite to that of the drift layer. With such a structure, when a reverse voltage is applied, the depletion layer around the outer peripheral groove is expanded due to the potential difference between the semiconductor material in the outer peripheral groove and the drift layer, thereby alleviating the electric field concentration at the corner of the anode electrode and making it difficult for insulation breakdown to occur.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-179815 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] An object of the present invention is to further relax the electric field generated in the drift layer when a reverse voltage is applied to a Schottky barrier diode using gallium oxide.

[0010] Means for solving technical problems

[0011] The Schottky barrier diode of the present invention comprises: a semiconductor substrate composed of gallium oxide; a drift layer composed of gallium oxide arranged on the semiconductor substrate; an anode electrode in Schottky contact with the drift layer; and a cathode electrode in ohmic contact with the semiconductor substrate, wherein the drift layer has a peripheral groove surrounding the anode electrode when viewed from above, the peripheral groove includes an inner peripheral wall, an outer peripheral wall, a bottom surface, an inner peripheral corner connecting the inner peripheral wall and the bottom surface, and an outer peripheral corner connecting the outer peripheral wall and the bottom surface, the inner peripheral wall and the inner peripheral corner of the peripheral groove are covered by the anode electrode via an insulating film, and the outer peripheral corner of the peripheral groove is covered by a semiconductor material of a conductivity type opposite to that of the drift layer.

[0012] According to the present invention, when a reverse voltage is applied, it is possible to relax the electric field generated around the inner corner portion of the outer peripheral trench in the drift layer.

[0013] In the present invention, the semiconductor material may be in a suspended state, thereby eliminating the need to supply a predetermined potential to the semiconductor material.

[0014] In the present invention, the drift layer may also have a plurality of central grooves surrounded by peripheral grooves and buried with anode electrodes. Thus, when a reverse voltage is applied, the mesa region between the central grooves becomes a depletion layer, and the channel region of the drift layer is pinched off, thereby significantly suppressing the leakage current when a reverse voltage is applied.

[0015] Effects of the Invention

[0016] As described above, according to the present invention, in a Schottky barrier diode using gallium oxide, when a reverse voltage is applied, the electric field generated in the drift layer can be further relaxed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 (a) is a schematic plan view showing the structure of the Schottky barrier diode 1 according to the first embodiment of the present invention. Figure 1 (b) is along Figure 1 (a) is a rough cross-sectional view of the line AA shown in FIG.

[0018] Figure 2 It is a schematic diagram for explaining the definition of the inner peripheral corner portion 36 and the outer peripheral corner portion 37 .

[0019] Figure 3 It is a graph showing the relationship between the electric field intensity applied to the drift layer 30 and the planar position when a reverse voltage of 1200 V is applied.

[0020] Figure 4 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode of a comparative example.

[0021] Figure 5It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 2 according to a second embodiment of the present invention.

[0022] Figure 6 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 3 according to a third embodiment of the present invention.

[0023] Figure 7 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 4 according to a fourth embodiment of the present invention.

[0024] Figure 8 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 5 according to a fifth embodiment of the present invention.

[0025] Fig. 9 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 6 according to a sixth embodiment of the present invention.

[0026] Fig.10 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 7 according to a seventh embodiment of the present invention.

[0027] Fig.11 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 8 according to an eighth embodiment of the present invention.

[0028] Fig.12 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 9 according to a ninth embodiment of the present invention.

[0029] Fig.13 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 10 according to a tenth embodiment of the present invention.

[0030] Fig.14 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 11 according to an eleventh embodiment of the present invention.

[0031] Fig.15 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 12 according to a twelfth embodiment of the present invention.

[0032] Fig.16 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 13 according to a thirteenth embodiment of the present invention.

[0033] Fig.17 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 14 according to a fourteenth embodiment of the present invention.

[0034] Fig.18 (a) is a schematic plan view showing the structure of a Schottky barrier diode 15 according to a fifteenth embodiment of the present invention. Fig.18(b) is along Fig.18 (a) is a rough cross-sectional view of the line AA shown in FIG.

[0035] Explanation of symbols

[0036] 1~15……Schottky barrier diode

[0037] 20...Semiconductor substrate

[0038] 21... Upper surface of semiconductor substrate

[0039] 22...Back side of semiconductor substrate

[0040] 30...Drift layer

[0041] 31... Upper surface of drift layer

[0042] 32...Peripheral groove

[0043] 33...Inner wall

[0044] 34...Outer wall

[0045] 35...Bottom

[0046] 36...Inner corner

[0047] 37...Outer peripheral corner

[0048] 38...Center groove

[0049] 39... Countertop area

[0050] 40... Anode electrode

[0051] 50……Cathode electrode

[0052] 60...Insulation film

[0053] 70...Semiconductor materials

[0054] 80... Field insulation film DETAILED DESCRIPTION

[0055] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0056] <First embodiment>

[0057] Figure 1 (a) is a schematic plan view showing the structure of the Schottky barrier diode 1 according to the first embodiment of the present invention. Figure 1 (b) is along Figure 1 (a) is a rough cross-sectional view of the line AA shown in FIG.

[0058] like Figure 1As shown in FIG. 1 , the Schottky barrier diode 1 of the first embodiment includes a semiconductor substrate 20 and a drift layer 30 both of which are made of gallium oxide (β-Ga2O3). Silicon (Si) or tin (Sn) is introduced into the semiconductor substrate 20 and the drift layer 30 as n-type doping. The doping concentration is higher in the semiconductor substrate 20 than in the drift layer 30, and thus the semiconductor substrate 20 is n-type. + The drift layer 30 acts as an n - The doping concentration of the semiconductor substrate 20 may be, for example, 1×10 18 cm -3 The doping concentration of the drift layer 30 is, for example, 1×10 16 cm -3 about.

[0059] The semiconductor substrate 20 is obtained by cutting a bulk crystal formed by a melt growth method or the like, and has a thickness of about 250 μm. The planar dimensions of the semiconductor substrate 20 are not particularly limited, and are usually selected according to the amount of current flowing in the element. If the maximum forward current is about 20 A, then the planar dimensions of about 2.4 mm×2.4 mm are sufficient when viewed from above.

[0060] The semiconductor substrate 20 has an upper surface 21 located on the upper surface side when mounted, and a back surface 22 located on the opposite side of the upper surface 21 and located on the lower surface side when mounted. A drift layer 30 is formed on the entire surface of the upper surface 21. The drift layer 30 is a thin film obtained by epitaxially growing gallium oxide on the upper surface 21 of the semiconductor substrate 20 using reactive sputtering, PLD method, MBE method, MOCVD method, HVPE method, etc. The film thickness of the drift layer 30 is not particularly limited, and is usually selected according to the reverse withstand voltage of the element. In order to ensure a withstand voltage of about 1200V, for example, about 10μm is sufficient.

[0061] On the upper surface 31 of the drift layer 30, an anode electrode 40 is formed in Schottky contact with the drift layer 30. The anode electrode 40 is composed of, for example, a metal such as platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), molybdenum (Mo), copper (Cu), etc. The anode electrode 40 can be a multilayer structure obtained by stacking different metal films, such as Pt / Au, Pt / Al, Pd / Au, Pd / Al, Pt / Ti / Au or Pd / Ti / Au. On the other hand, on the back side 22 of the semiconductor substrate 20, a cathode electrode 50 is provided in ohmic contact with the semiconductor substrate 20. The cathode electrode 50 is composed of, for example, a metal such as titanium (Ti). The cathode electrode 50 can be a multilayer structure obtained by stacking different metal films, such as Ti / Au or Ti / Al.

[0062] In the present embodiment, an annular peripheral groove 32 is provided on the upper surface 31 side of the drift layer 30. The peripheral groove 32 is formed by etching the drift layer 30 from the upper surface 31 side. The anode electrode 40 is provided in a region surrounded by the peripheral groove 32. The width of the peripheral groove 32 is, for example, about 10 μm, and the depth of the peripheral groove 32 is, for example, about 2 μm.

[0063] like Figure 1 As shown, the peripheral groove 32 includes an inner peripheral wall 33, an outer peripheral wall 34, a bottom surface 35, an inner peripheral corner 36 connecting the inner peripheral wall 33 and the bottom surface 35, and an outer peripheral corner 37 connecting the outer peripheral wall 34 and the bottom surface 35. The inner peripheral wall 33 and the outer peripheral wall 34 are inner wall surfaces of the peripheral groove 32 that are approximately parallel to the stacking direction, that is, approximately perpendicular to the upper surface 31 of the drift layer 30. The bottom surface 35 is an inner wall surface of the peripheral groove 32 that is approximately parallel to the upper surface 31 of the drift layer 30. The inner peripheral corner 36 is a portion connecting the inner peripheral wall 33 and the bottom surface 35, and the outer peripheral corner 37 is a portion connecting the outer peripheral wall 34 and the bottom surface 35. The inner peripheral corner 36 and the outer peripheral corner 37 may be approximately right angles or may be curved. In the case where the inner peripheral corner 36 and the outer peripheral corner 37 are curved, as shown in FIG. Figure 2 As shown, the curved surface between the inner peripheral wall 33 and the bottom surface 35 corresponds to the inner peripheral corner 36 , and the curved surface between the outer peripheral wall 34 and the bottom surface 35 corresponds to the outer peripheral corner 37 .

[0064] Moreover, in the Schottky barrier diode 1 of the present embodiment, the inner peripheral wall 33, the inner peripheral corner 36 and a part of the bottom surface 35 of the peripheral groove 32 are covered by the anode electrode 40 through the insulating film 60. In the peripheral groove 32, since the insulating film 60 is sandwiched between the anode electrode 40 and the drift layer 30, the anode electrode 40 and the drift layer 30 are not in direct contact. As the material of the insulating film 60, it is preferred to use an insulating material with a high dielectric constant such as HfO2 and Al2O3. In addition, the thickness of the insulating film 60 can be set to about 50nm, for example. According to these structures, the withstand voltage effect can be improved.

[0065] On the other hand, the outer peripheral wall 34, the outer peripheral corner 37 and the remaining portion of the bottom surface 35 of the outer peripheral groove 32 are covered in a manner of contacting with the semiconductor material 70 having a conductivity type opposite to that of the drift layer 30. In this embodiment, since the conductivity type of the drift layer 30 is n-type, the conductivity type of the semiconductor material 70 located in the outer peripheral groove 32 is p-type. Figure 1 In the example shown, the end surface position of the anode electrode 40 at the bottom surface 35 of the peripheral groove 32 coincides with the end surface position of the semiconductor material 70, so both are in contact. The film thickness of the semiconductor material 70 is, for example, 200 nm.

[0066] As p-type semiconductor materials constituting the semiconductor material 70, in addition to Si, GaAs, SiC, Ge, ZnSe, CdS, InP, SiGe, etc., p-type oxide semiconductors such as NiO, Cu2O, and Ag2O can also be listed. P-type oxide semiconductors have the advantage of not having oxidation problems. Among them, NiO is a special material that only exhibits p-type conductivity and is the most preferred material from the perspective of stabilizing quality. In addition, NiO has a relatively large band gap of 3.7 eV, so it is preferably a high-voltage material that effectively utilizes gallium oxide. Furthermore, in order to control the acceptor concentration, about 0.2 to 1.0 mol% of Li and La can be added to NiO (99.9%) as doping. The acceptor concentration is preferably 5×10 17 cm -3 From the perspective of manufacturing stability, 5×10 18 cm -3 Above, for example, 1×10 19 cm -3 This is because, when the acceptor concentration is low, there is a possibility that the semiconductor material 70 will be depleted and the required function cannot be obtained. Therefore, the higher the acceptor concentration, the better. However, when the acceptor concentration exceeds 1×10 22 cm -3 , the film properties may deteriorate, so it is preferably 5×10 21 cm -3 Left and right and below.

[0067] Here, if the p-type oxide constituting the semiconductor material 70 is in a completely amorphous state, it may unexpectedly crystallize during the heating process in device manufacturing, which may cause unstable characteristics. In view of this, when the p-type oxide is formed in the peripheral trench 32, for example, about 50% of the volume ratio is crystallized, thereby reducing the influence of crystallization during the heating process in device manufacturing.

[0068] Figure 3 is a graph showing the relationship between the electric field strength applied to the drift layer 30 and the plane position when a reverse voltage of 1200 V is applied. The solid line shows the characteristics of the Schottky barrier diode 1 obtained in this embodiment, and the dotted line shows Figure 4 The characteristics of the Schottky barrier diode obtained in the comparative example shown. Figure 4 The Schottky barrier diode obtained in the comparative example shown is different from the Schottky barrier diode 1 obtained in the present embodiment in that the entire inner wall of the peripheral trench 32 is covered with a semiconductor material 70 having a conductivity type opposite to that of the drift layer 30 .

[0069] like Figure 3As shown, at the plane position where the outer peripheral wall 34 is provided, there is no difference in the electric field strength between the Schottky barrier diode 1 obtained in the present embodiment and the Schottky barrier diode obtained in the comparative example, but at the plane position where the inner peripheral wall 33 is provided, the electric field strength of the Schottky barrier diode 1 obtained in the present embodiment is significantly reduced compared to the Schottky barrier diode obtained in the comparative example. In addition, the position where the local electric field strength between the inner peripheral wall 33 and the outer peripheral wall 34 becomes high corresponds to the boundary position between the anode electrode 40 and the semiconductor material 70 at the bottom surface 35.

[0070] As described above, according to the Schottky barrier diode 1 of the present embodiment, when a reverse voltage is applied, the electric field intensity applied to the vicinity of the inner peripheral wall 33 of the drift layer 30 can be relaxed.

[0071] <Second embodiment>

[0072] Figure 5 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 2 obtained in the second embodiment of the present invention.

[0073] like Figure 5 As shown, the Schottky barrier diode 2 obtained in the second embodiment is different from the Schottky barrier diode 1 in the first embodiment in that the peripheral trench 32 is buried with a field insulating film 80 in a manner covering the anode electrode 40 and the semiconductor material 70. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same reference numerals are given to the same elements, and repeated descriptions are omitted.

[0074] As the material of the field insulating film 80, various resins such as epoxy resin, acrylic resin such as polymethyl methacrylate, polyurethane, polyimide, polyvinyl alcohol, fluororesin, polyolefin, etc. can be used, and inorganic oxides or inorganic nitrides such as silicon oxide, aluminum oxide, silicon nitride can also be used. In the case of using a resin as the material of the field insulating film 80, a method of coating a resin solution and then drying it to form a resin film, a method of coating or evaporating a resin monomer and then polymerizing it, a method of performing a cross-linking treatment after film formation, etc. can be used. In addition, in the case of using an inorganic substance as the material of the field insulating film 80, it can be formed by a vacuum process such as a sputtering method and an evaporation method, or a solution process such as a sol-gel method.

[0075] As exemplified in this embodiment, the interior of the peripheral trench 32 may be buried with the field insulating film 80 .

[0076] <Third embodiment>

[0077] Figure 6 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 3 obtained in the third embodiment of the present invention.

[0078] like Figure 6 As shown, in the Schottky barrier diode 3 obtained in the third embodiment, a part of the semiconductor material 70 is placed on the anode electrode 40 at the bottom surface 35 of the peripheral groove 32, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0079] Such a structure is obtained by forming a stacked body of the insulating film 60 and the anode electrode 40 inside the peripheral trench 32 , and then forming the semiconductor material 70 inside the peripheral trench 32 .

[0080] As exemplified in this embodiment, a portion of the semiconductor material 70 may be formed on the anode electrode 40 .

[0081] <Fourth embodiment>

[0082] Figure 7 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 4 obtained in a fourth embodiment of the present invention.

[0083] like Figure 7 As shown, the Schottky barrier diode 4 obtained in the fourth embodiment has no hollow portion in the peripheral groove 32, and the peripheral groove 32 is entirely filled with a semiconductor material 70 except for the portion where the laminate of the insulating film 60 and the anode electrode 40 is formed, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same reference numerals are given to the same elements, and repeated descriptions are omitted.

[0084] Such a structure is obtained by forming a stack of the insulating film 60 and the anode electrode 40 inside the peripheral trench 32 and then filling the inside of the peripheral trench 32 with the semiconductor material 70 .

[0085] As exemplified in this embodiment, the entire peripheral trench 32 except for the portion where the stacked body of the insulating film 60 and the anode electrode 40 is formed may be buried with the semiconductor material 70 .

[0086] <Fifth embodiment>

[0087] Figure 8 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 5 obtained in the fifth embodiment of the present invention.

[0088] like Figure 8As shown, in the Schottky barrier diode 5 obtained in the fifth embodiment, a part of the anode electrode 40 is placed on the semiconductor material 70 at the bottom surface 35 of the peripheral groove 32, which is different from the Schottky barrier diode 1 in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0089] Such a structure is obtained by forming the semiconductor material 70 inside the peripheral trench 32 and then forming the anode electrode 40 inside the peripheral trench 32 .

[0090] As exemplified in this embodiment, a portion of the anode electrode 40 may be formed on the semiconductor material 70 .

[0091] <Sixth embodiment>

[0092] Fig. 9 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 6 obtained in a sixth embodiment of the present invention.

[0093] like Fig. 9 As shown, in the Schottky barrier diode 6 obtained in the sixth embodiment, there is no hollow portion in the peripheral groove 32, and the peripheral groove 32 is entirely buried by the anode electrode 40 except for the portion where the insulating film 60 and the semiconductor material 70 are formed, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0094] Such a structure is obtained by forming the insulating film 60 and the semiconductor material 70 inside the peripheral trench 32 and then burying the anode electrode 40 inside the peripheral trench 32 .

[0095] As exemplified in this embodiment, the entire peripheral trench 32 except for the portion where the insulating film 60 and the semiconductor material 70 are formed may be buried with the anode electrode 40 .

[0096] <Seventh embodiment>

[0097] Fig.10 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 7 according to a seventh embodiment of the present invention.

[0098] like Fig.10As shown, in the Schottky barrier diode 7 obtained in the seventh embodiment, a part of the laminate of the insulating film 60 and the anode electrode 40 is placed on the semiconductor material 70 at the bottom surface 35 of the peripheral trench 32, which is different from the Schottky barrier diode 1 in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same reference numerals are given to the same elements, and repeated descriptions are omitted.

[0099] Such a structure is obtained by forming the semiconductor material 70 inside the peripheral trench 32 and then forming a stacked body of the insulating film 60 and the anode electrode 40 inside the peripheral trench 32 .

[0100] As exemplified in this embodiment, a portion of the laminate of the insulating film 60 and the anode electrode 40 may be formed on the semiconductor material 70. In the case of such a structure, the semiconductor material 70 is not in contact with the anode electrode 40 on the bottom surface 35 of the peripheral groove 32. The potential of the semiconductor material 70 in this case is not particularly limited, and a predetermined fixed potential may be applied, or it may be in a floating state. In the latter case, since it is not necessary to supply a predetermined potential to the semiconductor material 70, the structure can be simplified.

[0101] <Eighth embodiment>

[0102] Fig.11 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 8 obtained in the eighth embodiment of the present invention.

[0103] like Fig.11 As shown, in the Schottky barrier diode 8 obtained in the eighth embodiment, a part of the semiconductor material 70 is placed on the insulating film 60 at the bottom surface 35 of the peripheral trench 32, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same reference numerals are given to the same elements, and repeated descriptions are omitted.

[0104] Such a structure is obtained by forming the insulating film 60 inside the peripheral trench 32 and then forming the semiconductor material 70 and the anode electrode 40 inside the peripheral trench 32 .

[0105] As exemplified in this embodiment, the lower surface of the semiconductor material 70 may be in contact with the upper surface of the insulating film 60 .

[0106] <Ninth embodiment>

[0107] Fig.12 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 9 obtained in the ninth embodiment of the present invention.

[0108] like Fig.12 As shown, in the Schottky barrier diode 9 obtained in the ninth embodiment, the boundary position of the laminated body of the insulating film 60 and the anode electrode 40 and the semiconductor material 70 is offset from the center of the bottom surface 35 of the peripheral groove 32 to the inner peripheral corner portion 36 side, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0109] In this case as well, if the inner corner portion 36 of the outer peripheral trench 32 is covered with the laminated body of the insulating film 60 and the anode electrode 40 , the same effect as that of the Schottky barrier diode 1 obtained in the first embodiment can be obtained.

[0110] <Tenth embodiment>

[0111] Fig.13 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 10 according to a tenth embodiment of the present invention.

[0112] like Fig.13 As shown, in the Schottky barrier diode 10 obtained in the tenth embodiment, the boundary position of the stacked body of the insulating film 60 and the anode electrode 40 and the semiconductor material 70 is offset from the center of the bottom surface 35 of the peripheral groove 32 to the peripheral corner portion 37 side, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0113] In this case as well, if the outer peripheral corner portion 37 of the outer peripheral trench 32 is covered with the semiconductor material 70 , the same effect as that of the Schottky barrier diode 1 obtained in the first embodiment can be obtained.

[0114] <11th embodiment>

[0115] Fig.14 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 11 obtained in the eleventh embodiment of the present invention.

[0116] like Fig.14 As shown, in the Schottky barrier diode 11 obtained in the eleventh embodiment, the upper portion of the peripheral wall 34 of the peripheral groove 32 is not covered by the semiconductor material 70 but exposed, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, so the same symbols are given to the same elements and repeated descriptions are omitted.

[0117] As exemplified in this embodiment, it is not essential that the entire outer peripheral wall 34 of the outer peripheral groove 32 is covered with the semiconductor material 70 , and at least the outer peripheral corner portion 37 may be covered with the semiconductor material 70 .

[0118] <Twelfth embodiment>

[0119] Fig.15 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 12 according to a twelfth embodiment of the present invention.

[0120] like Fig.15 As shown, in the Schottky barrier diode 12 obtained in the twelfth embodiment, a portion of the bottom surface 35 of the peripheral trench 32 is not covered by the laminated body of the insulating film 60 and the anode electrode 40 and the semiconductor material 70 and is exposed, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 in the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0121] As exemplified in this embodiment, it is not essential that the entire bottom surface 35 of the peripheral groove 32 is covered by the laminated body of the insulating film 60 and the anode electrode 40 or the semiconductor material 70 , and a portion of the bottom surface 35 may be exposed.

[0122] <Thirteenth embodiment>

[0123] Fig.16 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 13 obtained in the thirteenth embodiment of the present invention.

[0124] like Fig.16 As shown, in the Schottky barrier diode 13 obtained in the 13th embodiment, the peripheral trench 32 is buried by the field insulating film 80 in a manner covering the anode electrode 40 and the semiconductor material 70, which is different from the Schottky barrier diode 12 obtained in the 12th embodiment. The other basic structures are the same as those of the Schottky barrier diode 12 obtained in the 12th embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0125] In this embodiment, a portion of the bottom surface 35 of the peripheral trench 32 is exposed, so a portion of the field insulating film 80 is in contact with the bottom surface 35 of the peripheral trench 32. In this way, a portion of the field insulating film 80 may be in contact with the bottom surface 35 of the peripheral trench 32.

[0126] <Fourteenth embodiment>

[0127] Fig.17 It is a schematic cross-sectional view showing the structure of a Schottky barrier diode 14 obtained in the fourteenth embodiment of the present invention.

[0128] like Fig.17 As shown, in the Schottky barrier diode 14 obtained in the 14th embodiment, the end position of the anode electrode 40 is offset from the center of the bottom surface 35 of the peripheral groove 32 to the inner corner portion 36 side, thereby, a part of the insulating film 60 is not covered by the anode electrode 40 and is exposed, which is different from the Schottky barrier diode 1 of the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 of the first embodiment, so the same symbols are given to the same elements, and repeated descriptions are omitted.

[0129] In this case as well, if the inner peripheral wall 33 and the inner peripheral corner portion 36 of the outer peripheral trench 32 are covered with the laminated body of the insulating film 60 and the anode electrode 40 , the same effect as that of the Schottky barrier diode 1 obtained in the first embodiment can be obtained.

[0130] <Fifteenth embodiment>

[0131] Fig.18 (a) is a schematic plan view showing the structure of a Schottky barrier diode 15 according to a fifteenth embodiment of the present invention. Fig.18 (b) is along Fig.18 (a) is a rough cross-sectional view of the line AA shown in FIG.

[0132] like Fig.18 As shown, in the Schottky barrier diode 15 obtained in the fifteenth embodiment, a plurality of central trenches 38 are provided in the drift layer 30 in a manner surrounded by the peripheral trench 32, and the central trench 38 is buried by the anode electrode 40 via the insulating film 60, which is different from the Schottky barrier diode 1 obtained in the first embodiment. The other basic structures are the same as those of the Schottky barrier diode 1 obtained in the first embodiment, and therefore the same reference numerals are given to the same elements, and repeated descriptions are omitted.

[0133] The plurality of central grooves 38 are all arranged at positions overlapping the anode electrode 40 in a plan view. The area of ​​the drift layer 30 sandwiched by the peripheral grooves 32 or the central grooves 38 constitutes the mesa area 39. The peripheral grooves 32 surround the central grooves 38 and the mesa area 39 in an annular shape. The peripheral grooves 32 and the central grooves 38 do not need to be completely separated, and can be as Fig.18 As shown in (a), the central groove 38 is connected to the peripheral groove 32. The depths of the central groove 38 and the peripheral groove 32 may be the same or different. The mesa region 39 is a part of the drift layer 30 divided by the central groove 38 and the peripheral groove 32, and becomes a depletion layer when a reverse voltage is applied between the anode electrode 40 and the cathode electrode 50. As a result, the channel region of the drift layer 30 is pinched off, so that the leakage current when a reverse voltage is applied can be greatly limited.

[0134] As exemplified in this embodiment, the central trench 38 surrounded by the peripheral trench 32 may be provided in the drift layer 30 .

[0135] As mentioned above, although the preferred embodiment of the present invention has been described, the present invention is not limited to the above-mentioned embodiment, and various changes can be made within the scope without departing from the gist of the present invention, and these are of course included in the scope of the present invention.

Claims

1. A Schottky barrier diode, in, include: A semiconductor substrate composed of gallium oxide; A drift layer composed of gallium oxide disposed on the semiconductor substrate; an anode electrode in Schottky contact with the drift layer; and a cathode electrode in ohmic contact with the semiconductor substrate, The drift layer has a peripheral groove surrounding the anode electrode in a plan view, The peripheral groove includes an inner peripheral wall, an outer peripheral wall, a bottom surface, an inner peripheral corner portion connecting the inner peripheral wall and the bottom surface, and an outer peripheral corner portion connecting the outer peripheral wall and the bottom surface. The inner peripheral wall and the inner peripheral corner of the outer peripheral groove are covered by the anode electrode via an insulating film. The peripheral corner of the peripheral trench is covered with a semiconductor material having a conductivity type opposite to that of the drift layer.

2. The Schottky barrier diode according to claim 1, wherein: The semiconductor material is in a suspended state.

3. The Schottky barrier diode according to claim 1 or 2, wherein: The drift layer further has a plurality of central trenches which are surrounded by the peripheral trenches and in which the anode electrodes are buried.

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