A semiconductor device includes: a DLL circuit that generates an internal clock signal based on an external clock signal; a clock dividing circuit that generates two complementary internal clock signals having different phases based on the internal clock signal; and a multiplexer that outputs two internal data signals in synchronization with the two clock signals based on internal data signals, respectively. An internal power supply voltage supplied to the clock dividing circuit and an internal power supply voltage supplied to the multiplexer are generated by respective different power supply circuits and are separated from each other in the semiconductor device. This prevents interaction among noises.