Patent ID: 8471265

Claim:
An epitaxial substrate in which a group of group-III nitride layers are formed on a base substrate made of (111)-oriented single crystal silicon such that a (0001) crystal plane of said group of group-III nitride layers is substantially in parallel with a substrate surface of said base substrate, said epitaxial substrate comprising: a buffer layer formed of a first lamination unit and a second lamination unit being alternately laminated such that each of an uppermost portion and a lowermost portion of said buffer layer is formed of said first lamination unit; and a crystal layer formed on said buffer layer, wherein said first lamination unit includes: a composition modulation layer formed of a first unit layer and a second unit layer having different compositions being alternately and repeatedly laminated so that a compressive strain exists therein; and a first intermediate layer for enhancing said compressive strain existing in said composition modulation layer, said second lamination unit is a second intermediate layer that is substantially strain-free.