Patent ID: 8022427

Claim:
A nitride-based semiconductor device comprising: a substrate; a first step portion formed on a main surface side of a first side end surface of said substrate; a second step portion formed on said main surface side of a second side end surface substantially parallel to said first side end surface on an opposite side of said first side end surface; and a nitride-based semiconductor layer whose first side surface is a (000-1) plane starting from a first side wall of said first step portion and a second side surface starting from a second side wall of said second step portion on said main surface; wherein, said substrate includes a base substrate and an underlayer formed on said base substrate, said underlayer has a first crack and a second crack, a first inner side surface of said first crack is said first side wall and a second inner side surface of said second crack is said second side wall, said first side surface is formed starting from said first inner side surface and said second side surface is formed starting from said second inner side surface, said first crack and said second crack extend to the direction parallel to a (0001) plane of said underlayer and said main surface.