Patent ID: 8378386

Claim:
An epitaxial substrate for semiconductor device, comprising: a base substrate; a channel layer formed of a first group III nitride containing at least Al and Ga and having a composition of In x1 Al y1 Ga z1 N (x1+y1+z1=1); and a barrier layer including a near-surface portion and a base portion, the barrier layer being formed of a second group III nitride containing at least In and Al and having a composition of In x2 Al y2 Ga z2 N (x2+y2+z2=1), wherein: said near-surface portion is a portion positioned in a predetermined distance range from a surface of said barrier layer; said base portion is a portion of said barrier layer other than said near-surface portion; and an In composition ratio of the surface of said barrier layer is larger than an In composition ratio of said base portion.