To form a semiconductor device having an LDD structure adapted to microminiaturization with high withstand voltage by providing a second conductivity type high impurity concentration contact region in source and drain regions.

A gate oxide film 13 is extended from one end of a gate electrode 14 to one end of a LOCOS oxide film 12. When a width between the one end of the electrode 14 and one end of an electrode wiring 21 for a drain is W1, a width between the other end of the wiring 21 for the drain and the one end of the film 12 is W2, and a width of the wiring 21 for the drain is W3, n- type drain regions are respectively formed substantially directly under offset parts having widths W1 and W2, and an n+ type contact region 16 is provided substantially directly under the wiring 21 for the drain having the width W3. Accordingly, a device size can be further contracted by controlling the widths W1 and W2 of the offset parts of the film 13. And, a MOS device adapted to high integration with high withstand voltage is obtained.