Method of manufacturing semiconductor device

1. A method of manufacturing a semiconductor device, the method comprising:

preparing an n-type semiconductor substrate that comprises a first region and a second region in an upper surface of the semiconductor substrate, wherein the second region surrounds the first region;

forming a Schottky electrode at least on the first region of the upper surface of the semiconductor substrate such that the Schottky electrode is in Schottky-contact with the upper surface of the semiconductor substrate;

etching the second region of the upper surface of the semiconductor substrate such that the first region becomes higher than the second region, a rising surface is formed between the first region and the second region, and an outer peripheral edge of the Schottky electrode is located on the first region;

forming an insulating film on the upper surface of the semiconductor substrate, wherein the insulating film annularly extends along the rising surface, an inner peripheral edge of the insulating film is located on the Schottky electrode and an outer peripheral edge of the insulating film is located on the second region; and

forming a field plate electrode, wherein the field plate electrode is electrically connected with the Schottky electrode and faces the upper surface of the semiconductor substrate via the insulating film within an area extending from the outer peripheral edge of the Schottky electrode to the second region over the rising surface,

wherein the Schottky electrode is formed also on the second region of the upper surface in the forming of the Schottky electrode, and

a part of the Schottky electrode formed on the second region of the upper surface is also removed in the etching of the second region of the upper surface of the semiconductor substrate.

2. The method according to claim 1 , wherein

the semiconductor substrate is a substrate of oxide semiconductor, and

with a vacuum level as a reference, a Conduction Band Minimum (CBM) of the oxide semiconductor is lower than −4.0 eV and a Valence Band Maximum (VBM) of the oxide semiconductor is lower than −6.0 eV.

3. The method according to claim 1 , wherein the semiconductor substrate is a substrate of gallium oxide.

4. The method according to claim 1 , wherein the forming of the insulating film is performed by a mist CVD method.

5. The method according to claim 1 , wherein

the semiconductor substrate prepared in the preparing comprises an n-type drift layer and an n-type high resistivity layer that is lower in carrier density than the drift region, the high resistivity layer surrounds the drift region in the upper surface, and

a boundary of the first region and the second region is located in the high resistivity layer.

6. The method according to claim 5 , wherein the preparing of the semiconductor substrate comprises:

forming the drift layer by epitaxial growth;

etching a part of the drift layer to form a groove at a position where the high resistivity layer is to be formed; and

forming the high resistivity layer within the groove by epitaxial growth.

7. The method according to claim 6 , wherein the epitaxial growth of the high resistivity layer is performed by a mist CVD method.

8. The method according to claim 1 , further comprising:

performing an ion-implantation of impurities to the upper surface of the semiconductor substrate, the ion-implantation being performed between the etching of the second region and the forming of the insulating film,

wherein the ion-implantation is performed with a use of the Schottky electrode as a mask,

the impurities have a property of reducing carrier density of the semiconductor substrate, and

the impurities are implanted along a direction angled from a normal direction of the first region of the semiconductor substrate so as to be implanted under the Schottky electrode.

9. A method of manufacturing a semiconductor device, the method comprising:

preparing an n-type semiconductor substrate that comprises a first region and a second region in an upper surface of the semiconductor substrate, wherein the second region surrounds the first region;

forming a Schottky electrode at least on the first region of the upper surface of the semiconductor substrate such that the Schottky electrode is in Schottky-contact with the upper surface of the semiconductor substrate;

etching the second region of the upper surface of the semiconductor substrate such that the first region becomes higher than the second region, a rising surface is formed between the first region and the second region, and an outer peripheral edge of the Schottky electrode is located on the first region;

forming an insulating film on the upper surface of the semiconductor substrate, wherein the insulating film annularly extends along the rising surface, an inner peripheral edge of the insulating film is located on the Schottky electrode and an outer peripheral edge of the insulating film is located on the second region; and

forming a field plate electrode, wherein the field plate electrode is electrically connected with the Schottky electrode and faces the upper surface of the semiconductor substrate via the insulating film within an area extending from the outer peripheral edge of the Schottky electrode to the second region over the rising surface,

performing an ion-implantation of impurities to the upper surface of the semiconductor substrate, the ion-implantation being performed between the etching of the second region and the forming of the insulating film,

wherein the ion-implantation is performed with a use of the Schottky electrode as a mask,

the impurities have a property of reducing carrier density of the semiconductor substrate, and

the impurities are implanted along a direction angled from a normal direction of the first region of the semiconductor substrate so as to be implanted under the Schottky electrode.

10. The method according to claim 9 , wherein

the semiconductor substrate is a substrate of oxide semiconductor, and

with a vacuum level as a reference, a Conduction Band Minimum (CBM) of the oxide semiconductor is lower than −4.0 eV and a Valence Band Maximum (VBM) of the oxide semiconductor is lower than −6.0 eV.

11. The method according to claim 9 , wherein the semiconductor substrate is a substrate of gallium oxide.

12. The method according to claim 9 , wherein the forming of the insulating film is performed by a mist CVD method.