An object is to provide a semiconductor device with a novel structure. A semiconductor device includes a first transistor including a silicon region, a first gate insulating layer, a first gate electrode, and a first source electrode and a first drain electrode, a first insulating layer, a second insulating layer, a third insulating layer, and a second transistor, which includes an oxide semiconductor layer over the third insulating layer, a second source electrode and a second drain electrode, a second gate insulating layer, and a second gate electrode, and a fourth insulating layer and a fifth insulating layer. A first electrode passes through the first insulating layer and the second insulating layer to be electrically connected to the silicon region, and a second electrode passes through the third insulating layer, the fourth insulating layer and the fifth insulating layer to be electrically connected to the first electrode.