A semiconductor device comprises: a substrate; a first well region of a first conductivity type and a second well region of a second conductivity type formed horizontally adjacent to each other in the substrate; a buried insulation layer formed on the first well region and the second well region; a first semiconductor layer formed to vertically overlap the first well region, and a second semiconductor layer formed to vertically overlap the second well region, on the buried insulation layer; a first isolation layer formed between the first semiconductor layer and the second semiconductor layer on the buried insulation layer; and a conductive layer formed on the first semiconductor layer and the second semiconductor layer to extend over the first semiconductor layer and the second semiconductor layer.