Back-gate voltage control provides a high speed and low power consumption LSI operable in a wide temperature range in which a MOS transistor having back gates is used specifically according to operating characteristics of a circuit. In the LSI, an FD-SOI structure having an embedded oxide film layer is used and a lower semiconductor region of the embedded oxide film layer is used as a back gate. A voltage for back gates in logic circuits having a small load in logic circuit block is controlled in response to activation of the block from outside of the block. Transistors, in which the gate and the back gate are connected to each other, are used for the circuit generating the back gate driving signal, and logic circuits having a heavy load such as circuit block output section, and the back gates are directly controlled according to a gate input signal.