Semiconductor device

1. A semiconductor device, comprising:

a semiconductor layer containing a crystalline oxide semiconductor with a corundum structure as a major component; and

a Schottky electrode on the semiconductor layer,

the Schottky electrode comprising two or more metal layers and containing at least one metal selected from Group 4 of the periodic table.

2. The semiconductor device of claim 1 , comprising:

a first semiconductor layer;

a second semiconductor layer; and

a Schottky electrode on the first semiconductor layer, wherein

each of the first semiconductor layer and the second semiconductor layer contains a crystalline oxide semiconductor with a corundum structure as a major component, and

the first semiconductor layer has a carrier concentration less than a carrier concentration of the second semiconductor layer.

3. The semiconductor device of claim 1 , wherein the metal is a transition metal of the fourth period of the periodic table.

4. The semiconductor device of claim 1 , wherein the crystalline oxide semiconductor contains gallium or indium.

5. The semiconductor device of claim 1 , wherein the crystalline oxide semiconductor is α-Ga 2 O 3 or a mixed crystal thereof.

6. The semiconductor device of claim 1 , further comprising an ohmic electrode, wherein the ohmic electrode contains a metal of Group 4 or 11 of the periodic table.

7. The semiconductor device of claim 1 ,

wherein the semiconductor layer has a thickness of 40 μm or less.

8. The semiconductor device of claim 7 , wherein the semiconductor device shows capacitance of 1000 pF or less at 0 V bias when measured at 1 MHz.

9. The semiconductor device of claim 7 , wherein the semiconductor layer has a surface area of 1 mm 2 or less.

10. The semiconductor device of claim 7 , wherein the Schottky electrode has an area of 1 mm 2 or less.

11. The semiconductor device of claim 7 , wherein the semiconductor device is configured to be operated with current of 1 A or more.

12. The semiconductor device of claim 1 , wherein the semiconductor device is a power device.

13. The semiconductor device of claim 1 , wherein the semiconductor device is a power module, an inverter, or a converter.

14. The semiconductor device of claim 1 , wherein the two or more metal layers comprised in the Schottky electrode comprise a Ti layer.

15. The semiconductor device of claim 1 , wherein the two or more metal layers comprised in the Schottky electrode comprise a Pt layer.

16. The semiconductor device of claim 1 , wherein the two or more metal layers comprised in the Schottky electrode comprise an Au layer.

17. The semiconductor device of claim 14 , wherein the Ti layer is in a range of 1 nm to 500 μm in thickness.

18. A semiconductor system comprising: the semiconductor device of claim 1 .

19. A semiconductor device comprising:

a semiconductor layer comprising a crystalline oxide semiconductor with a corundum structure;

a Schottky electrode electrically connected to the semiconductor layer; and

an ohmic electrode electrically connected to the semiconductor layer,

the crystalline oxide semiconductor with the corundum structure of the semiconductor layer comprising gallium, and

the Schottky electrode comprising two or more metal layers and comprising at least one metal selected from among metals of Group 4 of the periodic table.

20. The semiconductor device of claim 19 , wherein

the semiconductor layer comprises a first semiconductor layer and a second semiconductor layer, and

the Schottky electrode is arranged on the first semiconductor layer.

21. The semiconductor device of claim 20 , wherein

the first semiconductor layer comprises a carrier concentration,

the second semiconductor layer comprises a carrier concentration, and

the carrier concentration of the first semiconductor layer is lower than the carrier concentration of the second semiconductor layer.