A semiconductor device includes a substrate, first, second, third and fourth bottom contacts in the substrate, and first, second, third and fourth active fins on respective ones of the first, second, third and fourth bottom contacts, the second and third fins overlapping in a first direction. First, second and third gate electrodes extend longitudinally in the first direction, the first and second gate electrodes disposed on side surfaces of respective ones of the first and fourth active fins and the third gate electrode disposed on side surfaces of the second and third active fins. A first top contact is on the first and second active fins and a second top contact is on the third and fourth active fins.