A semiconductor device prevents the ON current of a complementary field effect transistor from varying with changes in ambient temperature. The semiconductor device includes: a buffer circuit that generates a power-supply voltage of a CMOS; a first replica transistor that is a replica of a p-channel MOS transistor forming the CMOS, and is diode-connected; a second replica transistor that is a replica of an n-channel MOS transistor forming the CMOS, and is diode-connected; and a voltage controller that controls the voltage between the anode and cathode of the replica transistors so that the current value of the current flowing into the replica transistor becomes equal to a given target value. In this semiconductor device, the buffer circuit generates the power-supply voltage, with the target voltage being a voltage that is controlled by the voltage controller.