Patent ID: 6906345

Claim:
A semiconductor integrated circuit device comprising: one or more first MOSFETs driven by a first power supply voltage, each first MOSFET comprising a semiconductor substrate, a first gate oxide film formed on the semiconductor substrate, a first polycrystalline silicon gate electrode formed over the first gate oxide film, buried oxide films buried in the semiconductor substrate on opposite sides of the first polycrystalline silicon gate electrode, and first source and drain regions formed in the semiconductor substrate directly over the buried oxide films; and one or more second MOSFETs driven by a second power supply voltage lower than the first power supply voltage, each second MOSFET comprising a second gate oxide film formed on the semiconductor substrate and having a smaller thickness than the first gate oxide film, a second polycrystalline silicon gate electrode formed on the second gate oxide film, and second source and drain regions provided in the semiconductor substrate on opposite sides of the second polycrystalline silicon gate electrode.