A semiconductor device includes an on-die termination circuit, a clock input unit, a clock phase mixing unit, and a data input/output unit. The on-die termination circuit is configured to calibrate a resistance of a termination pad and output an impedance matching code. The clock input unit is configured to receive a data clock. The clock phase mixing unit is configured to receive the data clock through the clock input unit and a delayed data clock, which is generated by delaying the data clock by a predetermined time, mix a phase of the data clock and a phase of the delayed data clock at a ratio corresponding to the impedance matching code, and output a phase-mixed data clock. The data input/output unit is configured to input/output a data signal in response to the phase-mixed data clock.