Patent ID: 7119378

Claim:
A nitride semiconductor device comprising: a n-type semiconductor layer, p-type semiconductor layer and an active layer of a quantum well structure that is sandwiched between said p-type and n-type nitride semiconductor layer, wherein said active layer includes a first barrier layer, a second barrier layer and a third barrier layer; said first barrier layer being the nearest to said p-type nitride semiconductor layer among the first, second and third barrier layers; said second barrier layer being the nearest to said n-type nitride semiconductor layer among the first, second and third barrier layers; said third barrier layer being between said first and second barrier layers, and wherein said third barrier layer includes at least an upper barrier layer that is in contact with a p-side surface of said well layer and a lower barrier layer that is in contact with an n-side surface of said well layer; said upper and lower barrier layers being different in a composition or impurity concentration with each other.