A semiconductor device has a first semiconductor layer including a first circuit, a second semiconductor layer disposed on the first semiconductor layer and having a second circuit, and a via extending through portions of the first and second semiconductor layers and by which the first and second circuits are electrically connected. One of the circuits is a logic circuit and the other of the circuits is a memory circuit. The semiconductor device is manufactured by fabricating transistors of the logic and memory circuits on respective substrates, stacking the substrates, and electrically connecting the logic and memory circuits with a via.