Field MOS transistor and semiconductor integrated circuit including the same

摘要

A field MOS transistor having a high withstand voltage is disclosed. An island region of an epitaxial layer is surrounded by a heavily-doped isolation layer and a lightly-doped isolation layer formed thereon. A channel region is formed in the island region so as to assume the same doping level as that of the lightly-doped isolation layer. A region is formed below the island region so as to assume the same doping level as that of the heavily-doped isolation layer, thus supplying a back gate voltage to the transistor. The channel formation region is formed simultaneously with formation of the lightly-doped isolation layer, and the region below the island region is formed simultaneously with the heavily-doped isolation layer. As a result, manufacturing processes can be simplified.