Patent ID: 8884307

Claim:
A nitride semiconductor wafer comprising: a silicon substrate having a major surface; a lower strain relaxation layer provided on the major surface and including a nitride semiconductor, the lower strain relaxation layer having a first lattice constant; an intermediate layer provided on the lower strain relaxation layer 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 provided on the lower strain relaxation layer and including a nitride semiconductor, the first lower layer having a second lattice constant larger than the first lattice constant; a first doped layer provided on the first lower layer and including a nitride semiconductor, the first doped layer having a third lattice constant larger than the second lattice constant 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 fourth lattice constant larger than the third lattice constant and larger than the second lattice constant.