Abstract: A semiconductor integrated circuit has a DLL circuit for receiving a first control signal and generating a second control signal synchronized with the first control signal by carrying out a phase synchronization process. The semiconductor integrated circuit has a power supply circuit. The power supply circuit keeps the power supply voltage at a specific voltage level and supplies the power supply voltage only to the DLL circuit. Therefore, the DLL circuit can generate an internal clock which is stable and accurately synchronized with an external clock without including jitter.