A semiconductor device with a small variation in transistor characteristics is provided. The semiconductor device includes an oxide semiconductor, a first conductor and a second conductor over the oxide semiconductor, a first insulator in contact with a top surface of the first conductor, a second insulator in contact with a top surface of the second conductor, a third insulator which is positioned over the first insulator and the second insulator and has an opening overlapping with a region between the first conductor and the second conductor, a fourth insulator positioned over the oxide semiconductor and in the region between the first conductor and the second conductor, and a third conductor over the fourth insulator. Each of the first insulator and the second insulator is a metal oxide including an amorphous structure.