A change in electrical characteristics is inhibited and reliability is improved in a semiconductor device using a transistor including an oxide semiconductor. One embodiment of a semiconductor device including a transistor includes a gate electrode, first and second insulating films over the gate electrode, an oxide semiconductor film over the second insulating film, and source and drain electrodes electrically connected to the oxide semiconductor film. A third insulating film is provided over the transistor and a fourth insulating film is provided over the third insulating film. The third insulating film includes oxygen. The fourth insulating film includes nitrogen. The amount of oxygen released from the third insulating film is 1×1019/cm3 or more by thermal desorption spectroscopy, which is estimated as oxygen molecules. The amount of oxygen molecules released from the fourth insulating film is less than 1×1019/cm3.