Electrical characteristics of a semiconductor device including the oxide semiconductor are improved. Furthermore, a highly reliable transistor with small variation in electrical characteristics is manufactured. An oxynitride insulating film functioning as a base insulating film and a transistor in contact with the oxynitride insulating film are provided. The transistor includes an oxide semiconductor film in contact with the oxynitride insulating film functioning as a base insulating film. The total amount of gas having a mass-to-charge ratio of 30 released from the oxynitride insulating film by heat treatment and double of the amount of a gas having a mass-to-charge ratio of 32 released from the oxynitride insulating film by heat treatment is greater than or equal to 5×1015/cm2 and less than or equal to 5×1016/cm2, or greater than or equal to 5×1015/cm2 and less than or equal to 3×1016/cm2.