A semiconductor device, including: a semiconductor substrate having a first well region; an insulating layer formed on a first portion of the semiconductor substrate, and contacted with the first well region; a semiconductor layer formed on the insulating layer; an element isolation region reaching to an inside of the first well region, in a cross-sectional view; a first gate electrode layer formed on a first portion of the semiconductor layer via a first gate insulating film; a second gate electrode layer formed on both a second portion of the semiconductor layer via a second gate insulating film and a first portion of the element isolation region; an interlayer insulating film covering the first gate electrode layer, the second gate electrode layer and a second portion of the element isolation region; a first plug conductor layer formed in the interlayer insulating film.