A delay locked loop (DLL) of a semiconductor device includes: a first delay line for delaying a first clock signal in synchronization with a first edge of an external clock signal to output a first delayed clock signal; a second delay line for delaying a second clock signal in synchronization with a second edge of the external clock to output a second delayed clock signal; a duty cycle corrector (DCC) for mixing phases of the first and second delayed clock signals to output a DLL clock signal with a corrected duty cycle; and a DCC controller for disabling the duty cycle corrector in a section during which a phase difference between the first and second delayed clock signals is greater than a preset time after a delay locking.