Schottky barrier diode

Abstract

To provide a Schottky barrier diode capable of having a high breakdown voltage by using a Ga2O3 material, reducing a leakage current, and reducing a loss in a forward direction.SOLUTION: An n-type semiconductor substrate 10 including an n-type Ga2O3-based material and having an n-type semiconductor layer 12 and an n-type semiconductor region 13 having an impurity concentration higher than that of the n-type semiconductor layer 12, a plurality of p-type semiconductor portions 20 disposed on a surface of the n-type semiconductor substrate 10 or on the surface of the n-type semiconductor substrate 10, and an anode electrode 30 disposed on the surface of the n-type semiconductor substrate 10 and the p-type semiconductor portions 20, the n-type semiconductor region 13 being disposed at least in a region of the n-type semiconductor substrate 10 in contact with the anode electrode 30 between the adjacent p-type semiconductor portions 20, the Schottky barrier diode 1 is in contact with a part of the bottom of the p-type semiconductor portion 20 in a cross-sectional view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a Schottky barrier diode. [Background technology]

[0002] In recent years, Ga2O3-based materials have been attracting attention as semiconductor materials. Because Ga2O3-based materials have a very high critical electric field value Ec, semiconductor devices using Ga2O3-based materials have the potential to become semiconductor devices with high breakdown voltage.

[0003] However, when attempting to manufacture Schottky barrier diodes using Ga2O3-based materials, there are problems such as the extremely high critical electric field value Ec, which lowers the Schottky barrier due to image forces and increases leakage current, and the high critical electric field value Ec makes the Schottky barrier thinner, which increases leakage current due to thermonic emission, thermonic field emission, and field emission due to the tunneling effect, making it impossible to obtain sufficient reverse surge resistance.

[0004] To overcome this issue, it is conceivable to reduce the surface electric field by introducing the MPS (JBS) structure that has been applied to Schottky barrier diodes made of silicon-based materials. Here, a Schottky barrier diode (conventional Schottky barrier diode 800) made of a silicon-based material with an MPS (JBS) structure will be described. The conventional Schottky barrier diode 800 is made of a silicon-based material and includes a semiconductor substrate 810 having an n-type substrate layer 811, an n-type semiconductor layer 812, and a plurality of p-type semiconductor regions 820 formed on the surface of the n-type semiconductor layer 812, an anode electrode 830 in contact with the p-type semiconductor region 820, and a cathode electrode 840 (see FIG. 6(a); see, for example, Patent Document 1).

[0005] In the conventional Schottky barrier diode 800, by introducing the MPS (JBS) structure, depletion layers generated at the pn junction between the adjacent p-type semiconductor region 820 and n-type semiconductor layer 812 are pinched off, and the region with the maximum electric field can be pushed downward (directly below the p-type semiconductor region 820) from the surface of the semiconductor substrate 810. Therefore, it is thought that the surface electric field of the semiconductor substrate 810 can be reduced, and leakage current can be reduced. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2-151067 Summary of the Invention [Problem to be solved by the invention]

[0007] However, Ga2O3-based materials cannot form acceptors with shallow energy levels that are activated at room temperature, and holes are hardly injected into them. Therefore, even if an attempt is made to manufacture a Schottky barrier diode with an MPS (JBS) structure using Ga2O3-based materials, the p-type semiconductor region 820 hardly contributes to conduction, reducing the effective area of ​​the Schottky barrier diode and increasing forward loss.

[0008] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a Schottky barrier diode that uses a Ga2O3-based material and has a high breakdown voltage, is capable of reducing leakage current, and is capable of reducing forward loss. [Means for solving the problem]

[0009] The Schottky barrier diode of the present invention comprises an n-type semiconductor substrate made of an n-type Ga2O3-based material, the n-type semiconductor substrate having an n-type semiconductor layer and an n-type semiconductor region formed on the surface of the n-type semiconductor layer and having a higher impurity concentration than the n-type semiconductor layer; a plurality of p-type semiconductor parts arranged on or on the surface of the n-type semiconductor substrate; and an anode electrode arranged on the surfaces of the n-type semiconductor substrate and the p-type semiconductor parts so as to be in contact with the p-type semiconductor parts and the n-type semiconductor region, wherein the n-type semiconductor region is arranged at least in a region of the n-type semiconductor substrate that is in contact with the anode electrode between adjacent p-type semiconductor regions, and is in contact with a part of the bottom of the p-type semiconductor part in a cross-sectional view. [Effects of the Invention]

[0010] The Schottky barrier diode of the present invention includes an n-type semiconductor substrate made of a Ga2O3-based material, and therefore can utilize Ga2O3-based materials with high critical electric field values, making it possible to realize a semiconductor device with high breakdown voltage.

[0011] Furthermore, the Schottky barrier diode of the present invention includes a plurality of p-type semiconductor portions disposed on or at the surface of an n-type semiconductor substrate, so that depletion layers generated from the n-type semiconductor region and the p-type semiconductor portions pinch off each other, and the region with the maximum electric field (the region where avalanche breakdown occurs) can be pushed down from the surface of the n-type semiconductor substrate to just below the p-type semiconductor portions (see region R in FIG. 1, which will be described later). Therefore, the surface electric field of the n-type semiconductor substrate can be reduced, and leakage current can be reduced.

[0012] The Schottky barrier diode of the present invention includes an n-type semiconductor substrate having an n-type semiconductor region formed on the surface of an n-type semiconductor layer and having a higher impurity concentration than the n-type semiconductor layer, the n-type semiconductor region being disposed at least in a region of the n-type semiconductor substrate between adjacent p-type semiconductor regions and in contact with an anode electrode. This configuration allows the n-type semiconductor region to have a lower resistance than the n-type semiconductor layer, thereby increasing the amount of current flowing from the anode electrode through the n-type semiconductor region and the n-type semiconductor layer to the cathode electrode. This compensates for the decrease in current flow resulting from the p-type semiconductor portion barely contributing to conduction, preventing the forward loss of the Schottky barrier diode as a whole from increasing. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a Schottky barrier diode 1 according to a first embodiment. [Figure 2] 1 is a graph showing a concentration profile of the Schottky barrier diode 1 according to embodiment 1. In the figure, A-A', B-B', and C-C' correspond to the dashed dotted lines A-A', B-B', and C-C' in FIG. [Figure 3] 2 is a schematic graph shown to explain the reverse characteristics of the Schottky barrier diode 1 according to the first embodiment. [Figure 4] 2 is a schematic graph shown to explain the forward characteristics of the Schottky barrier diode 1 according to the first embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing a Schottky barrier diode 2 according to a second embodiment. [Figure 6] 6(a) and 6(b) are cross-sectional views showing a conventional Schottky barrier diode 800 and a Schottky barrier diode 801, respectively, in which the conventional Schottky barrier diode 800 is made of a Ga2O3-based material. Reference numeral 830 denotes an anode electrode, and reference numeral 840 denotes a cathode electrode. [Figure 7] FIG. 1 is a cross-sectional view showing a Schottky barrier diode 900 having a conventional MOS-SBD structure. DETAILED DESCRIPTION OF THE INVENTION

[0014] The Schottky barrier diode of the present invention will be described below based on the embodiments shown in the drawings. Note that the embodiments described below do not limit the invention according to the claims. Furthermore, not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0015] [Embodiment 1] 1. Configuration of Schottky barrier diode 1 according to embodiment 1 As shown in FIG. 1, the Schottky barrier diode 1 according to the first embodiment includes an n-type semiconductor substrate 10, a plurality of p-type semiconductor sections 20, an anode electrode 30, and a cathode electrode 40.

[0016] The n-type semiconductor substrate 10 is made of an n-type Ga2O3-based material and has an n-type substrate layer 11, an n-type semiconductor layer 12, and an n-type semiconductor region 13. A plurality of trenches 14 are formed in the surface of the n-type semiconductor substrate 10, and a p-type semiconductor portion 20 is disposed inside each trench 14.

[0017] In this specification, when a component is described as "made of... material," it does not mean that the component is made of only the pure material, but that it may contain trace amounts of impurities (donors, etc.).

[0018] The n-type substrate layer 11 is ++ The cathode electrode 40 is connected to the Ga2O3-based material.

[0019] The n-type semiconductor layer 12 is formed on the upper surface of the n-type substrate layer 11. + The n-type semiconductor layer 12 is an epitaxial layer made of a Ga2O3-based material. The n-type semiconductor layer 12 contains donor impurities such as Si and Sn.

[0020] The n-type semiconductor region 13 is formed on the surface of the n-type semiconductor layer 12. The n-type semiconductor region 13 is disposed between adjacent p-type semiconductor portions 20, and is disposed at least over the entire region of the n-type semiconductor substrate 10 that contacts the anode electrode 30. The n-type semiconductor region 13 is disposed between adjacent p-type semiconductor portions 20, from the region of the n-type semiconductor substrate 10 that contacts the anode electrode 30 (the surface of the n-type semiconductor substrate 10) to a depth deeper than the depth position of the bottom of the trench 14. In the depth region deeper than the depth position of the bottom of the trench 14, the n-type semiconductor region 13 extends horizontally to below the p-type semiconductor portion 20. Therefore, the n-type semiconductor region 13 contacts at least a portion of the bottom of the p-type semiconductor portion 20 when viewed in cross section.

[0021] A plurality of n-type semiconductor regions 13 are formed, and adjacent n-type semiconductor regions 13 are spaced apart from each other. Specifically, the end of the bottom of the p-type semiconductor portion 20 is in contact with the n-type semiconductor region 13, and the bottom of the central portion of the p-type semiconductor portion 20 is arranged so as to be in direct contact with the n-type semiconductor layer 12.

[0022] The impurity concentration of the n-type semiconductor region 13 is lower than the impurity concentration of the n-type semiconductor layer 12. The n-type semiconductor region 13 can be formed by implanting impurities into a specific region of the n-type semiconductor layer 12, but it can also be formed by forming a trench in the specific region of the n-type semiconductor layer 12 and depositing a Ga2O3-based material having a higher impurity concentration than the n-type semiconductor layer 12 in the trench.

[0023] Here, the concentration profile in the depth direction of the n-type semiconductor substrate 10 will be described with reference to the graph of FIG.

[0024] In the concentration profile of the impurity concentration along the depth direction of the n-type semiconductor region 13, the impurity concentration in the central part (in the depth direction) of the n-type semiconductor region 13 is higher than the impurity concentration in the surface and bottom parts of the n-type semiconductor region 13 (see FIG. 2). That is, the concentration profile of the impurity concentration along the depth direction of the n-type semiconductor region 13 has a substantially normal distribution centered on the central part.

[0025] In the concentration profile of the impurity concentration along the depth direction of the n-type semiconductor region 13, the peak impurity concentration of the concentration profile along the depth direction in the surface of the n-type semiconductor substrate 10 or in a region where the p-type semiconductor portion 20 is not formed on the surface (see the graph of the solid line A-A' in Figure 2) is higher than the peak impurity concentration of the concentration profile along the depth direction in the surface of the n-type semiconductor substrate 10 or in a region where the p-type semiconductor portion 20 is formed on the surface (see the graph of the dashed line B-B' in Figure 2).

[0026] Furthermore, the depth position of the peak of the concentration profile along the depth direction of the n-type semiconductor region 13 in the region where the p-type semiconductor portion 20 is not formed on the surface or on the surface (see the graph of the solid line A-A' in Figure 2) is different from the depth position of the peak of the concentration profile along the depth direction of the n-type semiconductor region 13 in the region where the p-type semiconductor portion 20 is formed on the surface or on the surface (see the graph of the dashed line B-B' in Figure 2), and is at a shallower depth position.

[0027] The p-type semiconductor portion 20 is made of a NiO-based material, a CuO-based material, a CuO-based material, or a SnO-based material (p-type oxide semiconductor material). The p-type semiconductor portion 20 can be formed by depositing a p-type oxide semiconductor material inside the trench 14 on the surface of the n-type semiconductor layer 12. A hetero pn junction is formed between the p-type semiconductor portion 20 and the n-type semiconductor region 13.

[0028] The anode electrode 30 is disposed on the surfaces of the n-type semiconductor substrate 10 and the p-type semiconductor portion 20 so as to be in contact with the p-type semiconductor portion 20 and the n-type semiconductor region 13. In the anode electrode 30, a Schottky barrier metal is formed in the lower layer, and a laminated film of, for example, Ti, Ni, and Au is formed in the upper layer. A Schottky junction is formed between the Schottky barrier metal and the n-type semiconductor region 13. The anode electrode 30 may also be formed of a single layer of Schottky barrier metal.

[0029] The cathode electrode 40 is a metal film formed on the surface of the n-type substrate layer 11.

[0030] Next, the reverse characteristics of the Schottky barrier diode 1 will be described using the graph in Fig. 3. Fig. 3 is a graph schematically showing the reverse characteristics of Example A1 (Schottky barrier diode 1 according to embodiment 1), Comparative Example A2 (MPS structure), and Comparative Example A3 (MOS-SBD structure). In Fig. 3, the reverse characteristics of Example A1 are shown by a solid line, the reverse characteristics of Comparative Example A2 are shown by a dashed line, and the reverse characteristics of Comparative Example A3 are shown by a dashed line.

[0031] Example A1 is a Schottky barrier diode having a configuration similar to that of the Schottky barrier diode 1 according to embodiment 1. Comparative example A2 is a Schottky barrier diode in which the conventional Schottky barrier diode 800 is made of a Ga2O3-based material (see FIG. 6(b)). Comparative example A3 is a Schottky barrier diode having a MOS-SBD structure made of a Ga2O3-based material (described later).

[0032] In order to take advantage of the advantages of using Ga2O3-based materials that have a wide band gap and are capable of withstanding high voltages, the impurity concentrations of the n-type substrate layer 11 and the n-type semiconductor layer 12 are made higher in Example A1 compared to when they are made of Si-based materials, and in Comparative Examples A2 and A3, the impurity concentrations of the n-type substrate layers 811, 911 and the n-type semiconductor layers 812, 912 are also made higher compared to when they are made of Si-based materials (see Figure 6(a)) as in Example A1.

[0033] Here, the details of Comparative Example A3 will be described. As shown in Fig. 7, the Schottky barrier diode 900 having a MOS-SBD structure of Comparative Example A3 has a structure in which a trench 914 is formed in the surface of an n-type semiconductor substrate 910 made of a Ga2O3-based material, a metal constituting an anode electrode 930 is also disposed inside the trench 914, and a high-k oxide film 950 (hafnium oxide film) is formed along the edge of the trench 914. In Fig. 7, reference numeral 911 denotes an n-type substrate layer, reference numeral 912 denotes an n-type semiconductor layer, and reference numeral 940 denotes a cathode electrode.

[0034] 3, even when a relatively large voltage is applied in the reverse direction, the reverse current Ir in Example A1 remains low up to a certain voltage. This is thought to be because the depletion layers generated at the pn junctions between the adjacent p-type semiconductor portion 20 and n-type semiconductor substrate 10 extend and pinch off the relatively thinly doped n-type semiconductor layer 12, thereby reducing the surface electric field and, as a result, reducing the leakage current.

[0035] On the other hand, in Comparative Example A2, the reverse current Ir increases as a relatively large voltage is applied in the reverse direction. This is thought to be because, by using a Ga2O3-based material, the impurity concentrations of n-type substrate layer 811 and n-type semiconductor layer 812 are higher than when using a Si-based material, and therefore the depletion layers generated from the pn junctions between adjacent p-type semiconductor region 820 and n-type semiconductor base 810 (n-type semiconductor layer 812) are less likely to extend and are less likely to be pinched off.

[0036] In Comparative Example A3, the reverse current Ir remains low up to a certain voltage, as in Example A1. This is thought to be because the trench shortens the surface spacing, and the high-k oxide film 950 weakens the electric field, reducing the surface electric field and, as a result, reducing the leakage current.

[0037] Next, the forward characteristics of the Schottky barrier diode 1 will be described using the graph in Fig. 4. Fig. 4 is a graph schematically showing the forward characteristics of Example A1 (Schottky barrier diode 1 according to embodiment 1), Comparative Example A2 (MPS structure), and Comparative Example A3 (MOS-SBD structure). Note that in Fig. 4 as well, the forward characteristics of Example A1 are shown by a solid line, the forward characteristics of Comparative Example A2 are shown by a dashed line, and the forward characteristics of Comparative Example A3 are shown by a dashed line.

[0038] As shown in FIG. 4, when a voltage is applied in the forward direction, the slope of the forward current If (the reciprocal of the resistance value) with respect to the forward voltage Vf in Example A1 is large. Therefore, it can be seen that Example A1 has a small resistance value and a small forward loss. This is because, although the p-type semiconductor section 20 hardly contributes to conduction, the resistance value of the n-type semiconductor region 13, which has a higher impurity concentration than the n-type semiconductor layer 12, is reduced, thereby increasing the amount of current flowing from the anode electrode through the n-type semiconductor region and the n-type semiconductor layer to the cathode electrode. This is thought to be because it is possible to compensate for the decrease in the amount of current due to the p-type semiconductor section hardly contributing to conduction, and it is possible to prevent the forward loss of the Schottky barrier diode as a whole from increasing.

[0039] On the other hand, the slope of the forward current If with respect to the forward voltage Vf (the reciprocal of the resistance value) in Comparative Example A2 is larger than that in Example A1, and the resistance value is larger than that in Example A1, resulting in larger forward loss. This is thought to be because the p-type semiconductor region 820 in Comparative Example 1 hardly contributes to conduction, reducing the effective area of ​​the Schottky barrier diode and increasing forward loss.

[0040] Furthermore, the slope of the forward current If with respect to the forward voltage Vf (the reciprocal of the resistance value) in Comparative Example A3 is larger than those in Example A1 and Comparative Example A2, and the resistance value is larger and the forward loss is larger than those in Example A1 and Comparative Example A2. This is thought to be because in Comparative Example A2, the high-k oxide film 950 is formed along the edge of the trench 914, so holes are not supplied from the metal in the trench 914 to the n-type semiconductor layer, resulting in a smaller forward current.

[0041] 2. Effects of the Schottky Barrier Diode 1 According to the First Embodiment The Schottky barrier diode 1 according to the first embodiment includes an n-type semiconductor substrate 10 made of a Ga2O3-based material, which makes it possible to utilize a Ga2O3-based material having a high critical electric field value, thereby realizing a semiconductor device with a high breakdown voltage.

[0042] Furthermore, the Schottky barrier diode 1 according to the first embodiment includes a plurality of p-type semiconductor portions 20 disposed on or at the surface of the n-type semiconductor substrate 10, so that depletion layers generated from the n-type semiconductor region 13 and the p-type semiconductor portions 20 pinch off each other, and the region with the maximum electric field can be pushed down from the surface of the n-type semiconductor substrate 10 to just below the p-type semiconductor portions 20 (see region R in FIG. 1 ). Therefore, the surface electric field of the n-type semiconductor substrate 10 can be reduced, and leakage current can be reduced.

[0043] The Schottky barrier diode 1 according to the first embodiment includes an n-type semiconductor substrate 10 having an n-type semiconductor region 13 formed on the surface of an n-type semiconductor layer 12 and having a higher impurity concentration than the n-type semiconductor layer 12, and the n-type semiconductor region 13 is disposed at least in a region of the n-type semiconductor substrate 10 that contacts the anode electrode 30 between adjacent p-type semiconductor sections 20. With this configuration, the resistance value of the n-type semiconductor region 13 is reduced, thereby increasing the amount of current that flows from the anode electrode 30 through the n-type semiconductor region 13 and the n-type semiconductor layer 12 to the cathode electrode 40. This makes it possible to compensate for the decrease in the amount of current that occurs when the p-type semiconductor section 20 makes almost no contribution to conduction, thereby reducing forward loss in the Schottky barrier diode as a whole.

[0044] Furthermore, in the Schottky barrier diode 1 according to the first embodiment, in the impurity concentration profile along the depth direction, the impurity concentration in the central portion (in the depth direction) of the n-type semiconductor region 13 is higher than the impurity concentrations in the surface and bottom portions of the n-type semiconductor region 13. Therefore, at the surface of the n-type semiconductor region 13 where the impurity concentration is low, a depletion layer is likely to extend during reverse bias, which makes it easier to reduce the surface electric field and thus makes it less likely for leakage current to occur. Furthermore, at the central portion of the n-type semiconductor region 13, which is the current path of the forward current, the impurity concentration is high, which reduces the resistance value of the n-type semiconductor region 13.

[0045] Furthermore, in the Schottky barrier diode 1 according to the first embodiment, in the concentration profile of the impurity concentration along the depth direction, the peak impurity concentration of the n-type semiconductor region 13 in the region where the p-type semiconductor section 20 is not formed on the surface of the n-type semiconductor substrate 10 is higher than the peak impurity concentration of the n-type semiconductor region 13 in the region where the p-type semiconductor section 20 is formed on the surface of the n-type semiconductor substrate 10. This reduces the resistance of the n-type semiconductor region 13 in the region where the p-type semiconductor section 20 is not formed, which is the current path of the forward current, making it easier to maintain the amount of forward current. As a result, the forward loss of the Schottky barrier diode as a whole can be reduced.

[0046] Furthermore, in the Schottky barrier diode 1 according to embodiment 1, in the concentration profile of the impurity concentration along the depth direction, the depth position of the peak of the n-type semiconductor region 13 in the region where the p-type semiconductor section 20 is formed on the surface of the n-type semiconductor substrate 10 is different from the depth position of the peak of the n-type semiconductor region 13 in the region where the p-type semiconductor section 20 is not formed on the surface of the n-type semiconductor substrate 10. Therefore, the impurity concentration at the boundary between the p-type semiconductor section 20 and the n-type semiconductor region 13 can be lowered, and electric field concentration at the bottom of the p-type semiconductor section 20 can be alleviated.

[0047] In a semiconductor substrate using a Ga2O3-based material, the effective mass of holes is extremely heavy and the mobility is nearly zero, making it difficult to form a p-type semiconductor region in an n-type semiconductor substrate by diffusion. In contrast, in the Schottky barrier diode 1 according to embodiment 1, multiple trenches 14 are formed in the surface of an n-type semiconductor substrate 10, and a p-type semiconductor portion 20 is disposed inside each trench 14. Therefore, it is possible to form a p-type semiconductor region in a semiconductor substrate using a Ga2O3-based material, in which it is difficult to form a p-type semiconductor region in an n-type semiconductor substrate by diffusion.

[0048] Furthermore, the Schottky barrier diode 1 according to the first embodiment has a plurality of n-type semiconductor regions 13 as the n-type semiconductor region 13, the adjacent n-type semiconductor regions 13 being spaced apart from one another, the depth position of the bottom of each of the n-type semiconductor regions 13 being deeper than the depth position of the bottom of the trench 14, and the bottom of the p-type semiconductor section 20 being disposed so as to be in direct contact with the n-type semiconductor layer 12, so that the bottom of the p-type semiconductor section 20 can serve as an avalanche generation region, making it easier to collect holes generated via the p-type semiconductor section 20. Furthermore, because the bottom of the p-type semiconductor section 20 is in direct contact with the n-type semiconductor layer 12, holes in the n-type semiconductor layer 12 can also be easily collected via the p-type semiconductor section 20.

[0049] [Embodiment 2] The Schottky barrier diode 2 according to the second embodiment basically has the same configuration as the Schottky barrier diode 1 according to the first embodiment, but the configuration of the p-type semiconductor portion is different from that of the Schottky barrier diode 1 according to the first embodiment. That is, no trench is formed in the n-type semiconductor substrate 10a, and the p-type semiconductor portion 20a is disposed on the n-type semiconductor substrate 10a (see FIG. 5).

[0050] The p-type semiconductor portion 20a can be formed by depositing a p-type oxide semiconductor material on the surface of the n-type semiconductor substrate 10a.

[0051] As in the first embodiment, adjacent n-type semiconductor regions 13a are spaced apart, and the center of the bottom of the p-type semiconductor portion 20a is in contact with the n-type semiconductor layer 12. In the second embodiment, the n-type semiconductor regions 13 are formed by implanting n-type impurities to a predetermined depth and diffusing them.

[0052] As described above, the Schottky barrier diode 2 according to the second embodiment differs from the Schottky barrier diode 1 according to the first embodiment in the configuration of the p-type semiconductor portion. However, like the Schottky barrier diode 1 according to the first embodiment, the Schottky barrier diode 2 includes an n-type semiconductor substrate 10a made of a Ga2O3-based material. This makes it possible to utilize a Ga2O3-based material having a high critical electric field value, thereby enabling the realization of a semiconductor device having a high breakdown voltage.

[0053] Furthermore, the Schottky barrier diode 2 according to the second embodiment includes a plurality of p-type semiconductor portions 20a disposed on the surface of the n-type semiconductor substrate 10a, so that depletion layers generated in the n-type semiconductor region 13a and the p-type semiconductor portions 20a pinch off each other, and the region with the maximum electric field can be pushed down from the surface of the n-type semiconductor substrate 10a to just below the p-type semiconductor portions 20a. This reduces the surface electric field of the n-type semiconductor substrate 10a, and reduces leakage current.

[0054] The Schottky barrier diode 2 according to the second embodiment includes an n-type semiconductor substrate 10a having an n-type semiconductor region 13a formed on the surface of an n-type semiconductor layer 12 and having a higher impurity concentration than the n-type semiconductor layer 12, with the n-type semiconductor region 13a being disposed over at least the entire region of the n-type semiconductor substrate 10a that contacts the anode electrode 30. With this configuration, the resistance of the n-type semiconductor region 13a is reduced, thereby increasing the amount of current that flows from the anode electrode 30 through the n-type semiconductor region 13a and the n-type semiconductor layer 12 to the cathode electrode 40. This compensates for the reduction in the amount of current that occurs when the p-type semiconductor portion 20a makes little contribution to conduction, thereby reducing forward loss throughout the Schottky barrier diode as a whole.

[0055] Furthermore, in the Schottky barrier diode 2 according to the second embodiment, the p-type semiconductor portion 20a is disposed on the surface of the n-type semiconductor base 10a, so that the step of forming a trench can be omitted.

[0056] The Schottky barrier diode 2 according to the second embodiment has the same configuration as the Schottky barrier diode 1 according to the first embodiment except for the configuration of the p-type semiconductor portion, and therefore has the corresponding effects of the Schottky barrier diode 1 according to the first embodiment.

[0057] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment and can be embodied in various forms without departing from the spirit of the present invention, and for example, the following modifications are also possible.

[0058] (1) The positions, connections, numbers, etc. described in the above embodiments (including each modified example; the same applies below) are examples and can be changed within the scope that does not impair the effects of the present invention.

[0059] (2) In the second embodiment, the n-type semiconductor region 13 is formed by implanting and diffusing n-type impurities at a predetermined depth, but the present invention is not limited to this. The n-type impurities may be implanted near the surface of the n-type semiconductor substrate and diffused therein, or may be implanted and diffused at a position deeper than the p-type semiconductor portion 20. In either case, the n-type semiconductor region 13 is separated from the bottom of the p-type semiconductor portion 20 near the bottom thereof, and the n-type semiconductor region 13 is in contact with a portion of the bottom of the p-type semiconductor portion 20, while the bottom of the central portion of the p-type semiconductor portion 20 is in direct contact with the n-type semiconductor layer 12. [Explanation of symbols]

[0060] 1, 2... Schottky barrier diode, 10, 10a... n-type semiconductor substrate, 12... n-type semiconductor layer, 13, 13a... n-type semiconductor region, 14... trench, 20, 20a... p-type semiconductor portion, 30... anode electrode

Claims

1. n-type Ga ２ O ３ an n-type semiconductor substrate made of a silicon-based material, the n-type semiconductor substrate having an n-type semiconductor layer and an n-type semiconductor region formed on a surface of the n-type semiconductor layer and having a higher impurity concentration than the n-type semiconductor layer; a plurality of p-type semiconductor portions disposed on or at the surface of the n-type semiconductor substrate; an anode electrode disposed on the surfaces of the n-type semiconductor substrate and the p-type semiconductor portion so as to be in contact with the p-type semiconductor portion and the n-type semiconductor region; the n-type semiconductor region is disposed at least in a region of the n-type semiconductor substrate between adjacent p-type semiconductor portions that contacts the anode electrode, and is in contact with a portion of a bottom of the p-type semiconductor portion when viewed in cross section.

2. 2. The Schottky barrier diode according to claim 1, wherein in a concentration profile of the impurity concentration along the depth direction, the impurity concentration in a central portion of the n-type semiconductor region is higher than the impurity concentrations in a surface and a bottom portion of the n-type semiconductor region.

3. 2. The Schottky barrier diode according to claim 1, wherein, in a concentration profile of the impurity concentration along the depth direction, a peak impurity concentration of the n-type semiconductor region in a region on the surface of the n-type semiconductor substrate where the p-type semiconductor portion is not formed or on the surface is higher than a peak impurity concentration of the n-type semiconductor region in a region on the surface of the n-type semiconductor substrate where the p-type semiconductor portion is formed or on the surface.

4. 2. The Schottky barrier diode according to claim 1, wherein, in a concentration profile of an impurity concentration along a depth direction, a depth position of a peak of the n-type semiconductor region in a region where the p-type semiconductor portion is not formed on the surface of the n-type semiconductor substrate or on the surface is different from a depth position of a peak of the n-type semiconductor region in a region where the p-type semiconductor portion is formed on the surface of the n-type semiconductor substrate or on the surface.

5. a plurality of trenches are formed in the surface of the n-type semiconductor substrate; the p-type semiconductor portion is disposed inside each of the trenches, The n-type semiconductor region has a plurality of n-type semiconductor regions, The adjacent n-type semiconductor regions are spaced apart from each other, a depth position of a bottom of each of the n-type semiconductor regions is deeper than a depth position of a bottom of the trench; 5. The Schottky barrier diode according to claim 1, wherein a bottom of the p-type semiconductor portion is disposed so as to be in direct contact with the n-type semiconductor layer.

6. a plurality of the p-type semiconductor portions are disposed on a surface of the n-type semiconductor substrate, The n-type semiconductor region has a plurality of n-type semiconductor regions, 5. The Schottky barrier diode according to claim 1, wherein the adjacent n-type semiconductor regions are spaced apart from each other, and the bottom of the p-type semiconductor portion is in direct contact with the n-type semiconductor layer.

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