Patent ID: 8384089

Claim:
A method of manufacturing a nitride semiconductor device, which comprises: a substrate; a nitride semiconductor layer formed on the substrate and having a heterojunction interface; and a recess portion formed on the nitride semiconductor layer, the method comprising; forming the nitride semiconductor layer by: forming a carrier transit layer, which has a composition represented by the formula: Al x1 In x2 Ga 1−x1−x2 N, wherein x1 satisfies 0≦x1<1, wherein x2 satisfies 0≦x2≦1, wherein x1+x2 satisfies 0≦x1+x2≦1; and forming a carrier supply layer by: forming a first layer on the carrier transit layer, said first layer having a composition represented by the formula: Al y Ga 1−y N, wherein y satisfies 0<y≦1 and x1<y; forming a second layer formed on the first layer, said second layer containing GaN; and forming a third layer formed on the second layer, said third layer having a composition represented by the formula: Al z Ga 1−z N, wherein z satisfies 0<z≦1 and x1<z, forming the recess portion to penetrate the third layer and expose a main surface of the second layer at a bottom portion of the recess portion, and forming a gate electrode on the exposed main surface of the second layer at the bottom portion of the recess portion.