US Patent 7714606 Semiconductor integrated circuit

A plurality of MOS transistors each having an SOI structure includes, in mixed form, those brought into body floating and whose body voltages are fixed and variably set. When a high-speed operation is expected in a logic circuit in which operating power is relatively a low voltage and a switching operation is principally performed, body floating may be adopted. Body voltage fixing may be adopted in an analog system circuit that essentially dislikes a kink phenomenon of a current-voltage characteristic. Body bias variable control may be adopted in a logic circuit that requires the speedup of operation in an active state and needs low power consumption in a standby state. Providing in mixed form the transistors which are subjected to the body floating and the body voltage fixing and which are variably controlled in body voltage, makes it easier to adopt an accurate body bias according to a circuit function and a circuit configuration in terms of the speedup of operation and the low power consumption.