Nitride semiconductor device

1. A nitride semiconductor device including a vertical transistor and a vertical diode, the nitride semiconductor device comprising:

a substrate;

a first nitride semiconductor layer of a first conductivity type above the substrate;

a second nitride semiconductor layer of a second conductivity type above the first nitride semiconductor layer, the second conductivity type being different from the first conductivity type;

a first opening penetrating through the second nitride semiconductor layer to the first nitride semiconductor layer;

a second opening provided away from the first opening and penetrating through the second nitride semiconductor layer to the first nitride semiconductor layer;

an electron transport layer and an electron supply layer provided, in stated order from a substrate side, along an inner face of each of the first opening and the second opening and above the second nitride semiconductor layer;

a gate electrode of the vertical transistor above the electron supply layer and covering the first opening;

an anode electrode of the vertical diode above the electron supply layer and covering the second opening;

a third opening provided between the first opening and the second opening in a plan view and penetrating through the electron supply layer and the electron transport layer to the second nitride semiconductor layer;

a source electrode of the vertical transistor connected to the second nitride semiconductor layer and a portion of each of the electron supply layer and the electron transport layer on a first opening side, in the third opening;

a drain electrode of the vertical transistor provided on a side of the substrate facing away from the first nitride semiconductor layer, at a position where the drain electrode overlaps the gate electrode in a plan view; and

a cathode electrode of the vertical diode on the side of the substrate facing away from the first nitride semiconductor layer, at a position where the cathode electrode overlaps the anode electrode in a plan view,

wherein the anode electrode and the source electrode are electrically connected, and

the cathode electrode and the drain electrode are electrically connected.

2. The nitride semiconductor device according to claim 1 , further comprising:

a first threshold adjustment layer between the gate electrode and the electron supply layer; and

a second threshold adjustment layer between the anode electrode and the electron supply layer.

3. The nitride semiconductor device according to claim 2 ,

wherein the first threshold adjustment layer and the second threshold adjustment layer are each a nitride semiconductor layer of the second conductivity type.

4. The nitride semiconductor device according to claim 2 ,

wherein the second threshold adjustment layer has a thickness less than a thickness of the first threshold adjustment layer.

5. The nitride semiconductor device according to claim 1 ,

wherein the anode electrode is connected to a portion of each of the electron supply layer and the electron transport layer on a second opening side, in the third opening.

6. The nitride semiconductor device according to claim 1 ,

wherein the source electrode is further connected to a portion of each of the electron supply layer and the electron transport layer on a second opening side, in the third opening.

7. The nitride semiconductor device according to claim 1 , comprising:

a plurality of vertical transistors each of which is the vertical transistor, and a plurality of vertical diodes each of which is the vertical diode,

wherein the plurality of vertical transistors and the plurality of vertical diodes are alternately disposed in a plan view.

8. The nitride semiconductor device according to claim 1 , comprising:

a plurality of vertical transistors each of which is the vertical transistor, and a plurality of vertical diodes each of which is the vertical diode,

wherein the plurality of vertical transistors are disposed adjacent to each other in a first region in a plan view, and

the plurality of vertical diodes are disposed adjacent to each other in a second region in a plan view, the second region being different from the first region.