The semiconductor device includes an internal clock generator, a shift signal generator and a first control signal generator. The internal clock generator generates a first internal clock signal and a second internal clock signal in response to an external clock signal. The shift signal generator shifts a clock enable signal in response to the first internal clock signal to generate first and second shift signals, and the shift signal generator shifts the clock enable signal in response to the second internal clock signal to generate third and fourth shift signals. The first control signal generator generates a first control signal in response to the first and third shift signals.