High voltage soi semiconductor device

An SOI-type semiconductor device, interposed insulating layer laminated to the semiconductor substrate and the first semiconductor layer as an active layer, while on the surface of the first semiconductor layer, a second semiconductor layer and the second semiconductor layer has different conductivity type third semiconductor layer are formed of different conductivity type fourth semiconductor layer and the first semiconductor layer on the interface of the first insulating layer and the semiconductor layer. The fourth semiconductor layer is set such impurity per unit area of ​​greater than 3 × 10