A voltage-controlled oscillator is provided. A semiconductor device includes a first circuit and a second circuit. The first circuit has a function of holding a first potential and a function of controlling the level of a third potential supplied to the second circuit according to a second potential based on the first potential. The second circuit has a function of outputting a second signal based on a first signal input to the second circuit. The delay time from input of the first signal to the second circuit to output of the second signal from the second circuit is determined by the third potential.