A semiconductor device includes a substrate; a first transistor formed over the substrate; a second transistor formed over the first transistor; a third transistor formed over the substrate; and a fourth transistor formed over the third transistor. The first, second, third, and fourth transistor include first, second, third, and fourth gate electrodes, respectively, and include first, second, third, and fourth source regions and first, second, third, and fourth drain region of first, second, third, and fourth conductivity types, respectively. The first conductivity type is different from the second conductivity type. The third conductivity type is the same as the fourth conductivity type. The first and second gate electrodes are integrated, and the third and fourth gate electrode are integrated.