In a related-art semiconductor device, there is a problem that a second-order harmonic distortion originating in a power amplifier driven by a rectangular-wave signal cannot be effectively suppressed. According to an embodiment, a semiconductor device generates a transmission signal RF_OUT for driving an antenna by receiving first transmission pulses INd_P and second transmission pulses INd_N having a duty ratio lower than 50%, adjusting a phase difference between the first and second transmission pulses INd_P and INd_N to a predefined phase difference, and supplying the phase-difference-adjusted first and second transmission pulses INd_P and INd_N to a power amplifier 54.