The semiconductor device includes a memory cell including a first transistor including a first channel formation region, a first gate electrode, and first source and drain regions; a second transistor including a second channel formation region provided so as to overlap with at least part of either of the first source region or the first drain region, a second source electrode, a second drain electrode electrically connected to the first gate electrode, and a second gate electrode; and an insulating layer provided between the first transistor and the second transistor. In a period during which the second transistor needs in an off state, at least when a positive potential is supplied to the first source region or the first drain region, a negative potential is supplied to the second gate electrode.