A semiconductor integrated circuit includes a frequency determining unit configured to determine an operational speed of the semiconductor integrated circuit and to generate a frequency region signal; a duty cycle control unit configured to detect a duty cycle of a DLL clock and to generate a duty cycle control signal; a duty cycle correcting unit configured to generate a corrected clock by correcting a duty cycle of an input clock in response to the frequency region signal and in response to the duty cycle control signal; and a DLL (Delay Locked Loop) circuit configured to generate the DLL clock by controlling a phase of the corrected clock.