Patent ID: 7462867

Claim:
A Group III nitride compound semiconductor device, comprising: a substrate consisting of a single layer, including a post and a trench, which includes at least one structure of a dot-like structure, a stripe-shaped structure, and a grid-like structure formed at an upper portion thereof and made of itself, said post and trench having a side wall perpendicular to a surface of said substrate; a buffer layer of a Group III nitride compound semiconductor uniformly formed on said post and on said trench of said substrate along a surface of said substrate, said buffer layer comprising a portion formed on said post and a portion formed in said trench and being a layer for growing a single crystal of Group III nitride compound semiconductor from said buffer layer; a first Group III nitride compound semiconductor layer having a uniform thickness and formed on said buffer layer along said post and said trench of said substrate, and comprising a single crystal portion formed on said post and a single crystal portion formed in said trench; and a second Group III nitride compound semiconductor layer formed on said first Group III nitride compound semiconductor layer, said second Group III nitride compound semiconductor layer being buried in said trench of said substrate and formed on said first Group III nitride compound semiconductor layer and having an upper surface which is uniformly flat, wherein said portion of said buffer layer which is formed on said post of said substrate, and said portion of said buffer layer which is formed in said trench of said substrate are separate.