A highly functional semiconductor device is provided. The semiconductor device includes a first transistor and a second transistor. The first transistor includes a first semiconductor layer, a first gate electrode, a first electrode, and a second electrode. The second transistor includes a second semiconductor layer, a second gate electrode, a third electrode, and a fourth electrode. The first gate electrode and the second gate electrode are connected to each other, and the second electrode and the third electrode are connected to each other. A first insulating layer, a second insulating layer, and a second semiconductor layer are stacked over the first semiconductor layer. The first insulating layer is less likely to diffuse hydrogen than the second insulating layer. The second insulating layer contains oxide, the first semiconductor layer contains polycrystalline silicon, and the second semiconductor layer contains a metal oxide. The first transistor is a p-channel transistor and the second transistor is an n-channel transistor.