A semiconductor device includes a first insulator, a transistor over the first insulator, a second insulator over the transistor, and a third insulator over the second insulator. The transistor includes an oxide semiconductor. The amount of oxygen released from the second insulator when converted into oxygen molecules is larger than or equal to 1×1014 molecules/cm2 and smaller than 1×1016 molecules/cm2 in thermal desorption spectroscopy at a surface temperature of a film of the second insulator of higher than or equal to 50° C. and lower than or equal to 500° C. The second insulator includes oxygen, nitrogen, and silicon.