Patent ID: 8791511

Claim:
A semiconductor device comprising: a second conductive type first semiconductor layer disposed on a first conductive type semiconductor substrate; a second conducive type drain region selectively formed on a surface layer of the first semiconductor layer; a first conductive type base region selectively formed on the surface layer of the first semiconductor layer so as to be away from the drain region; a first conductive type first well region selectively formed on the surface layer of the first semiconductor layer between the drain region and base region so as to be away from the drain region and in partial contact with the base region; a second conductive type source region selectively formed on a surface layer of the base region; and a gate electrode disposed via a gate dielectric film on a surface of the base region between the source region and first semiconductor layer, wherein the first well region includes first conductive type low concentration regions and first conductive type high concentration regions with a impurity concentration higher than that of the low concentration regions, and the high concentration regions are separated by the low concentration regions.