A semiconductor device includes a phase comparison circuit, an output enablement signal generation circuit, and a data input/output (I/O) circuit. The phase comparison circuit compares a phase of a clock signal with a phase of a delay locked loop (DLL) clock signal to generate a phase information signal. The output enablement signal generation circuit latches an internal command in response to a first pre-control signal and outputs the latched internal command as an output enablement signal in response to an operation clock signal and a second pre-control signal. The output enablement signal generation circuit generates the first pre-control signal according to an internal clock signal and an input clock signal. The data I/O circuit receives input data and output the received input data as output data synchronized with a strobe signal in response to the output enablement signal.