A device, including: a first layer of first transistors, overlaid by at least one interconnection layer, wherein the interconnection layer includes metals such as copper or aluminum; a second layer including second transistors, the second layer overlaying the interconnection layer, wherein the second layer is less than about 0.4 micron thick; and a connection path connecting the second transistors to the interconnection layer, wherein the connection path includes at least one through-layer via, and the through-layer via includes material whose co-efficient of thermal expansion is within about 50 percent of the second layer coefficient of thermal expansion.