A semiconductor device includes a swing level shifting unit configured to use a first power supply voltage as a power supply voltage, receive a CML clock swinging around a first voltage level, and shift a swing reference voltage level of the CML clock to a second voltage level lower than the first voltage level, and a CML clock transfer buffering unit configured to use a second power supply voltage as a power supply voltage and buffer the CML clock, which is transferred from the swing level shifting unit and swings around the second voltage level.