Patent ID: 7462884

Claim:
A nitride semiconductor device comprising: an active layer made of a nitride semiconductor and placed between an n-side nitride semiconductor layer and a p-side nitride semiconductor layer, and an n-side electrode disposed on the n-side nitride semiconductor layer and a p-side electrode disposed on the p-side nitride semiconductor layer, wherein the p-side nitride semiconductor layer comprises, from the active layer side, a p-side wide band gap layer made of a nitride semiconductor having a wider band gap than that of the active layer and containing a p-type impurity, and a three layer structure comprising a first p-side nitride semiconductor layer, a second p-side nitride semiconductor layer and a third p-side nitride semiconductor layer, wherein the third p-side nitride semiconductor layer contains a p-type impurity in a concentration of 5×10 20 to 2×10 21 cm −3 , the second p-side nitride semiconductor layer contains a p-type impurity in a lower concentration than that of the third p-side nitride semiconductor layer, and the first p-side nitride semiconductor layer has a narrower band gap than that of the second p-side nitride semiconductor layer, and has a lower p-type impurity concentration in the vicinity of the interface with the second p-side nitride semiconductor layer than a p-type impurity concentration of the second p-side nitride semiconductor layer.