A highly reliable semiconductor device is provided. The semiconductor device includes a gate electrode, a gate insulating film over the gate electrode, a semiconductor film overlapping with the gate electrode with the gate insulating film positioned therebetween, a source electrode and a drain electrode that are in contact with the semiconductor film, and an oxide film over the semiconductor film, the source electrode, and the drain electrode. An end portion of the semiconductor film is spaced from an end portion of the source electrode or the drain electrode in a region overlapping with the semiconductor film in a channel width direction. The semiconductor film and the oxide film each include a metal oxide including In, Ga, and Zn. The oxide film has an atomic ratio where the atomic percent of In is lower than the atomic percent of In in the atomic ratio of the semiconductor film.