A semiconductor device capable of level shifting in a negative potential direction using an n-channel transistor is provided. The semiconductor device includes a first source follower, a second source follower, and a comparator. The first source follower is supplied with a second high power supply potential and a low power supply potential; the second source follower is supplied with a first high power supply potential and the low power supply potential; and a digital signal which expresses a high level or a low level using the second high power supply potential or the first high power supply potential is input to the first source follower. Here, the second high power supply potential is a potential higher than the first high power supply potential, and the first high power supply potential is a potential higher than the low power supply potential. The comparator compares output potentials of the first source follower and the second source follower and outputs a digital signal which expresses a high level or a low level using the first high power supply potential or the low power supply potential.