Patent ID: 7161408

Claim:
A semiconductor integrated circuit device having a plurality of operation modes comprising: a logic circuit which is formed on a substrate and includes a first MIS transistor; a monitoring circuit, which is formed on the substrate and includes a second MIS transistor, to output an oscillating signal; a control circuit which receives a clock signal having a frequency according to one of the operation modes and the oscillating signal from the monitoring circuit and outputs a control signal to the logic circuit and the monitoring circuit; wherein a threshold voltage of the first MIS transistor and a threshold voltage of the second MIS transistor are controlled by the control signal from the control circuit; wherein the control circuit compares the frequency of the clock signal and the frequency of the oscillating signal and controls the control signal so as to synchronize the clock signal and the oscillating signal; and wherein the control signal controls a substrate bias voltage of the first MIS transistor and a substrate bias voltaae of the second MIS transistor.