Patent ID: 8247794

Claim:
A nitride semiconductor device comprising: a substrate having a plurality of protrusions formed in an in-plane direction on a first major surface, and a depression between adjacent ones of the protrusions; an Al x1 Ga 1-x1 N (0≦x1≦1) first buried layer formed on the depression and one of the protrusions of the substrate; an In y Al z Ga 1-y-z N (0<y≦1, 0≦z≦1) buried layer formed on the Al x1 Ga 1-x1 N first buried layer; and an Al x2 Ga 1-x2 N (0≦x2≦1) second buried layer formed on the In y Al z Ga 1-y-z N buried layer, wherein a portion of the Al x1 Ga 1-x1 N first buried layer formed on the depression and a portion of the Al x1 Ga 1-x1 N first buried layer formed on the one of the protrusions are not connected to each other, and a portion of the In y Al z Ga 1-y-z N buried layer formed above the depression and a portion of the In y Al z Ga 1-y-z N buried layer formed above the one of the protrusions are connected to each other.