The present invention provides a semiconductor device including a first terminal and a second terminal respectively coupled to both ends of a crystal resonator, an inverter circuit having an input coupled to the first terminal and an output coupled to the second terminal, a feedback resistor which couples between the first terminal and the second terminal, a variable capacitor coupled to at least one of the first and second terminals, and a control circuit. The control circuit performs control to increase both of the drive capability of the inverter circuit and the capacitance value of the variable capacitor in a second mode rather than a first mode.