A semiconductor device includes a terminal to which a touch electrode may be coupled; a source voltage drop circuit generating a constant voltage; a phase shift circuit generating a phase shifted clock in response to a first clock and a phase control signal; and a switching circuit to which the constant voltage is supplied. The switching circuit generates drive pulses for applying the constant voltage to the terminal in response to the phase shifted clock. The phase shift circuit varies the phase of the drive pulses based on the phase control signal.