Semiconductor device which comprises transistor and diode

1. A semiconductor device, comprising:

a substrate;

a transistor that comprises a first electron transit layer and an electron supply layer which are stacked in a thickness direction of the substrate;

a second electron transit layer formed above the first electron transit layer and the electron supply layer in parallel to the first electron transit layer and the electron supply layer;

an anode electrode that forms a Schottky junction with the second electron transit layer; and

a cathode electrode that forms an ohmic junction with the second electron transit layer, wherein

the anode electrode is connected to a source of the transistor, and

the cathode electrode is connected to a drain of the transistor,

wherein the transistor is located between the substrate and the second electron transit layer; and

the first electron transit layer and the electron supply layer are located between the substrate and the second electron transit layer, in the thickness direction of the substrate.

2. A semiconductor device, comprising:

a substrate;

a buffer layer formed above the substrate;

a first electron transit layer formed above the buffer layer;

an electron supply layer formed above the first electron transit layer;

a cap layer formed above the electron supply layer;

an insulating layer formed above the cap layer; and

a second electron transit layer formed above the insulating layer,

wherein the cap layer is located between the electron supply layer and the insulating layer, in the thickness direction of the substrate.

3. The semiconductor device according to claim 2 , wherein the cap layer is an n-type gallium nitride layer.

4. The semiconductor device according to claim 3 , further comprising:

a second n-type gallium nitride layer formed on the insulating layer,

wherein the insulating layer is made of an aluminum nitride or an aluminum gallium nitride.