A potential is held stably. A negative potential is generated with high accuracy. A semiconductor device with a high output voltage is provided. The semiconductor device includes a first transistor, a second transistor, a capacitor, and a comparator. The comparator includes a non-inverting input terminal, an inverting input terminal, and an output terminal. A gate and one of a source and a drain of the first transistor are electrically connected to each other. One of a source and a drain of the second transistor is electrically connected to the non-inverting input terminal of the comparator, one electrode of the capacitor, and a gate of the second transistor. The other of the source and the drain of the second transistor is electrically connected to the one of the source and the drain of the first transistor. The first transistor and the second transistor each contain an oxide semiconductor.