Patent ID: 6969887

Claim:
A semiconductor device comprising: a semiconductor substrate of a first conductivity type, which has a first major surface and a second major surface; a lightly-doped semiconductor layer of the first conductivity type, which is formed on the first major surface of the semiconductor substrate; a first semiconductor region of the first conductivity type, which is formed on a top of an island-shaped region on a surface of the lightly-doped semiconductor layer; a first electrode, which surrounds the first semiconductor region and is buried in the lightly-doped semiconductor layer to a deeper position than the first semiconductor region; a second semiconductor region which is formed on the second major surface of the semiconductor substrate; a buried field relaxation layer which is formed in the lightly-doped semiconductor layer between a bottom surface of the first electrode and the second semiconductor region, the buried field relaxation layer including a first field relaxation layer of the second conductivity type and second field relaxation layers of the first conductivity type formed at two ends of the first field relaxation layer; a second electrode which is formed on the first semiconductor region on the first major surface; and a third electrode which is formed on the second semiconductor region on the second major surface.