US Patent 7531880 Semiconductor device and manufacturing method thereof

A device includes a semiconductor layer on an insulating layer; a gate insulator on the semiconductor layer; a comb-shaped gate electrode on the gate insulator, including a base portion extending in a first direction and tooth portions extending in a second direction from one side surface of the base portion; a comb-shaped low-concentration diffusion layer in the semiconductor layer under the gate electrode having a first electroconductive type; a source layer in the semiconductor layer on the tooth portion side of the base portion having second electroconductive type with high concentration; a drain layer in the semiconductor layer on a side of the base portion opposite the tooth portion side having second electroconductive type with high concentration; and an extraction layer in the semiconductor layer between the source and the device isolating layers having first electroconductive type with high concentration, and connected with the diffusion layer.