A semiconductor device with favorable reliability is provided. The semiconductor device includes a first insulator; a second insulator positioned over the first insulator; an oxide positioned over the second insulator; a first conductor and a second conductor positioned apart from each other over the oxide; a third insulator positioned over the oxide, the first conductor, and the second conductor; a third conductor positioned over the third insulator and at least partly overlapping with a region between the first conductor and the second conductor; a fourth insulator positioned to cover the oxide, the first conductor, the second conductor, the third insulator, and the third conductor; a fifth insulator positioned over the fourth insulator; and a sixth insulator positioned over the fifth insulator. An opening reaching the second insulator is formed in at least part of the fourth insulator; the fifth insulator is in contact with the second insulator through the opening; and the first insulator, the fourth insulator, and the sixth insulator have a lower oxygen permeability than the second insulator.