A semiconductor device, including: a first semiconductor layer including first transistors, wherein the first transistors are interconnected by at least one metal layer including aluminum or copper; and a second mono-crystallized semiconductor layer including second transistors and overlaying the at least one metal layer, wherein the at least one metal layer is in-between the first semiconductor layer and the second mono-crystallized semiconductor layer, wherein the second mono-crystallized semiconductor layer is less than 100 nm in thickness, and wherein the second transistors include horizontally oriented transistors.