Patent ID: 7372086

Claim:
A semiconductor device comprising: a semiconductor substrate including a main surface; a MOSFET including a double gate structure provided on a side of the main surface of the semiconductor substrate, the double gate structure comprising top and bottom gate electrodes, the bottom gate electrode being located at a lower level than the main surface; an isolation region for isolating the MOSFET from other elements comprising a trench provided on the side of the main surface of the semiconductor substrate and an insulator provided in the trench, the isolation region having a region in the trench around the MOSFET, the region having a deeper bottom than other regions in the trench, and all of the region having the deeper bottom being covered with the top gate electrode; and a side gate electrode and a side gate insulating film provided in the region having the deeper bottom than the other regions in the trench around the MOSFET, wherein a part of the insulator is provided in the region having the deeper bottom than the other regions under the side gate electrode.