A semiconductor device including a transistor having an SOI structure the operating speed of which is not affected is provided. A MOS transistor having the SOI structure is formed which satisfies R·C·f<1 where C is a gate capacitance (F), R is a body resistance (Ω), f is a clock operating frequency...http://www.google.de/patents/US7129543?utm_source=gb-gplus-sharePatent US7129543 - Method of designing semiconductor device, semiconductor device and recording medium