A semiconductor device is provided, which comprises a rectifier circuit configured to generate a first voltage from a first signal inputted from an input terminal, a comparing circuit configured to compare a reference voltage and the first voltage inputted from the rectifier circuit and to output a second signal to a switch, and a voltage generation circuit configured to generate a second voltage from the first signal inputted from the input terminal. The rectifier circuit includes a transistor including at least a control terminal, and the voltage generation circuit inputs the second voltage to the control terminal when the switch is turned on in accordance with the second signal.