A first transistor including a channel formation region, a first gate insulating layer, a first gate electrode, and a first source electrode and a first drain electrode; a second transistor including an oxide semiconductor layer, a second source electrode and a second drain electrode, a second gate insulating layer, and a second gate electrode; and a capacitor including one of the second source electrode and the second drain electrode, the second gate insulating layer, and an electrode provided to overlap with one of the second source electrode and the second drain electrode over the second gate insulating layer are provided. The first gate electrode and one of the second source electrode and the second drain electrode are electrically connected to each other.