Patent ID: 8835983

Claim:
A nitride semiconductor device comprising: an intermediate layer formed on a major surface of a silicon substrate and including a nitride semiconductor; an upper strain relaxation layer provided on the intermediate layer and including a nitride semiconductor; and a functional layer provided on the upper strain relaxation layer and including a nitride semiconductor, the intermediate layer including: a first lower layer formed on the major surface and including a nitride semiconductor; a first doped layer provided on the first lower layer and including a nitride semiconductor, the first doped layer having a lattice constant larger than or equal to lattice constant of the first lower layer and containing an impurity at a concentration of 1×10 18 cm −3 or more and less than 1×10 21 cm −3 ; and a first upper layer provided on the first doped layer and including a nitride semiconductor, the first upper layer having a lattice constant larger than or equal to the lattice constant of the first doped layer and larger than the lattice constant of the first lower layer.