Semiconductor integrated circuit device and substrate bias controlling method

A semiconductor integrated circuit device includes: a first bias generating circuit, a second bias generating circuit and a control circuit. The first bias generating circuit generates a first substrate bias voltage of a P-channel transistor. The second bias generating circuit generates a second substrate bias voltage of N-channel transistor. The control circuit controls the first bias generating circuit and the second bias generating circuit independently on the basis of operating states of circuits to which the first substrate bias voltage and the second substrate bias voltage are applied.