Semiconductor device

1. A semiconductor device, comprising:

a substrate;

a semiconductor layer stacked body including a first nitride semiconductor layer above the substrate and a second nitride semiconductor layer which is on the first nitride semiconductor layer and has a band gap wider than a band gap of the first nitride semiconductor layer;

a gate electrode on the semiconductor layer stacked body;

a source electrode and a drain electrode located on opposite sides of the gate electrode and spaced apart from the gate electrode in a plan view of the semiconductor layer stacked body;

a first active region which has a first carrier layer located in the first nitride semiconductor layer, the source electrode, the drain electrode and the gate electrode being disposed in the first active region in the plan view;

a second active region which is on an extension of a long side of the drain electrode in the plan view, and has a second carrier layer located in the first nitride semiconductor layer, the second carrier layer being separated from the first carrier layer by an element isolation region containing no carrier;

a gate extraction electrode located opposite a short side of the drain electrode and disposed in the second active region in the plan view, and electrically connected with the gate electrode; and

a source extraction electrode directly on the semiconductor layer stacked body and disposed in the second active region in the plan view and electrically connected with the source electrode.

2. The semiconductor device according to claim 1 ,

wherein, in the plan view, no conductor is disposed on the semiconductor layer stacked body in a region between the drain electrode and the gate extraction electrode, and

in a cross-sectional view of the semiconductor layer stacked body, the drain electrode and the gate extraction electrode are opposed to each other having the region therebetween.

3. The semiconductor device according to claim 1 ,

wherein, in the plan view, no conductor is disposed on the semiconductor layer stacked body in a region between the drain electrode and the gate extraction electrode, and

in a cross-sectional view of the semiconductor layer stacked body, the second carrier layer is immediately under the gate extraction electrode.

4. The semiconductor device according to claim 1 ,

wherein, in a cross-sectional view of the semiconductor layer stacked body, the second carrier layer extends from a region under the source extraction electrode toward a side of the drain electrode beyond a region under the gate extraction electrode.

5. The semiconductor device according to claim 1 ,

wherein the gate extraction electrode is a first metal layer which is in Schottky contact with the second nitride semiconductor layer.

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

an insulating film on the second nitride semiconductor layer,

wherein the gate extraction electrode is a second metal layer on the insulating film.

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

a third nitride semiconductor layer on the second nitride semiconductor layer,

wherein the gate extraction electrode is a third metal layer which is on the third nitride semiconductor layer and in ohmic contact with the third nitride semiconductor layer.

8. The semiconductor device according to claim 7 ,

wherein the third nitride semiconductor layer is a p-type nitride semiconductor layer.

9. The semiconductor device according to claim 7 ,

wherein the source extraction electrode is a fifth metal layer which is in ohmic contact with the second nitride semiconductor layer.

10. The semiconductor device according to claim 9 , further comprising:

a second source extraction electrode between the source extraction electrode and the gate extraction electrode; and

a fifth nitride semiconductor layer on the second nitride semiconductor layer,

wherein the second source extraction electrode is a tenth metal layer on the fifth nitride semiconductor layer.

11. The semiconductor device according to claim 10 ,

wherein the fifth nitride semiconductor layer is a p-type nitride semiconductor layer.

12. The semiconductor device according to claim 9 , further comprising:

a second source extraction electrode between the source extraction electrode and the gate extraction electrode,

wherein the second source extraction electrode is a ninth metal layer which is in Schottky contact with the second nitride semiconductor layer.

13. The semiconductor device according to claim 7 ,

wherein the source extraction electrode is a sixth metal layer which is in Schottky contact with the second nitride semiconductor layer.

14. The semiconductor device according to claim 7 , wherein the semiconductor layer stacked body further includes:

a fourth nitride semiconductor layer on the second nitride semiconductor layer,

wherein the source extraction electrode is an eighth metal layer on the fourth nitride semiconductor layer.

15. The semiconductor device according to claim 14 ,

wherein the fourth nitride semiconductor layer is a p-type nitride semiconductor layer.

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

a third nitride semiconductor layer on the second nitride semiconductor layer,

wherein the gate extraction electrode is a fourth metal layer which is on the third nitride semiconductor layer and in Schottky contact with the third nitride semiconductor layer.

17. The semiconductor device according to claim 16 ,

wherein the third nitride semiconductor layer is a p-type nitride semiconductor layer.

18. The semiconductor device according to claim 1 ,

wherein, in the plan view, the second active region encloses the first active region via the element isolation region.

19. The semiconductor device according to claim 1 ,

wherein, the source extraction electrode is in ohmic contact with second nitride semiconductor layer.