The present invention provides a semiconductor device. In the semiconductor device, a signal distributor distributes a high frequency signal generated by an oscillator and inputted to an input part to first and second signals and outputs the same from first and second output parts respectively. A modulator modulates a baseband signal with the first signal and outputs the same therefrom. An offset adjustment unit compares the second signal and the first signal that leaks from the output of the modulator to thereby adjust an offset of the baseband signal. The signal distributor includes a first capacitive element provided between the input part and the first output part, and a second capacitive element provided between the first output part and the second output part. The electrostatic capacitance of the first capacitive element is larger than that of the second capacitive element.