A semiconductor device with high on-state current and high reliability is provided. The semiconductor device includes first to fifth insulators, first to third oxides, and first to fourth conductors; the fifth insulator includes an opening in which the second oxide is exposed; the third oxide is placed in contact with a bottom portion of the opening and a side portion of the opening; the second insulator is placed in contact with the third oxide; the third conductor is provided in contact with the second insulator; the third insulator is placed in contact with a top surface of the third conductor and the second insulator; and the fourth conductor is in contact with the third insulator and the top surface of the third conductor and placed in the opening.