A semiconductor device with a small variation in characteristics is provided. The semiconductor device includes a first insulator, a transistor over the first insulator, a second insulator over the transistor, a third insulator over the second insulator, a fourth insulator over the third insulator, and an opening region. The opening region includes the second insulator, the third insulator over the second insulator, and the fourth insulator over the third insulator. The third insulator includes an opening reaching the second insulator. The fourth insulator is in contact with a top surface of the second insulator inside the opening.