In a semiconductor device including an oxide semiconductor, the amount of oxygen vacancies is reduced. Moreover, electrical characteristics of a semiconductor device including an oxide semiconductor are improved. The semiconductor device includes a transistor including a gate electrode over a substrate, a gate insulating film covering the gate electrode, an oxide semiconductor film overlapping with the gate electrode with the gate insulating film provided therebetween, and a pair of electrodes in contact with the oxide semiconductor film; and over the transistor, a first insulating film covering the gate insulating film, the oxide semiconductor film, and the pair of electrodes; and a second insulating film covering the first insulating film. An etching rate of the first insulating film is lower than or equal to 10 nm/min and lower than an etching rate of the second insulating film when etching is performed at 25° C. with 0.5 weight % of hydrofluoric acid.