A semiconductor device includes first and second chips that are stacked such that first surfaces of their element layers face each other. Each chip has a substrate, an element layer on a first surface of the substrate, pads on the element layer, and vias that penetrate through the substrate and the element layer. Each via is exposed from a second surface of the substrate and directly connected to one of the pads. The vias include a first via of the first chip directly connected to a first pad of the first chip and a second via of the second chip directly connected to a second pad of the second chip. The pads further include a third pad of the second chip which is electrically connected to the second pad by a wiring in the element layer of the second chip and to the first pad through a micro-bump.