Patent ID: 7612604

Claim:
A semiconductor integrated circuit device, comprising: a bias generator to generate a first body bias voltage, a second body bias voltage and a third body bias voltage; a circuit module including at least a MOS transistor; a body bias switch circuit including a first MOS transistor to control supply of the first body bias voltage, a second MOS transistor to control supply of the second body bias voltage and a third MOS transistor to control supply of the third body bias voltage, respectively; and a switch controller to control the body bias switch circuit, wherein when the circuit module is in a first state, the switch controller to turn on the first MOS transistor of the body bias switch circuit to supply the first body bias voltage to a well of the MOS transistor of the circuit module; when the circuit module is in a second state, the switch controller to turn on the second MOS transistor of the body bias switch circuit to supply the second body bias to the well of the MOS transistor of the circuit module; and when the circuit module is in a third state, the switch controller to turn on the third MOS transistor of the body bias switch circuit to supply the third body bias voltage to the well of the MOS transistor of the circuit module, the switch controller to transmit a first request signal to the bias generator, and to receive a first acknowledge signal indicating that a bias signal generated by the bias generator has been stabilized, the switch controller to transmit a second request signal to the body bias switch circuit, and to receive a second acknowledge signal indicating that the control of the body bias switch circuit has been completed, and the switch controller to receive the first acknowledge signal and the second acknowledge signal and to transmit, to the circuit module, a control signal to start the operation of the circuit module.