A semiconductor device comprises a delay locked loop (DLL) configured to control a phase delay of an internal clock to output first and second DLL clocks; an output enable unit configured to generate rising/falling data output enable signals in response to the second DLL clocks; and an output driver configured to output data in response to one of the first DLL clocks selected by the rising/falling data output enable signals, where a phase of the second DLL clock leads that of the first DLL clock.