A device including a first layer of first transistors interconnected by at least one first interconnection layer, wherein the first interconnection layer includes copper or aluminum, a second layer including second transistors, the second layer overlaying the first interconnection layer, wherein the second layer is less than 2 micron thick, wherein the second layer has a coefficient of thermal expansion; and a connection path connecting at least one of the second transistors to the first interconnection layer, wherein the connection path includes at least one through-layer via, and wherein the through-layer via includes material whose co-efficient of thermal expansion is within 50 percent of the second layer coefficient of thermal expansion.