A semiconductor device, the device including: a first silicon layer including a first single crystal silicon; a first metal layer over the first silicon layer; a second metal layer over the first metal layer; a first level including a plurality of transistors over the second metal layer, where the plurality of transistors include a second single crystal silicon; a third metal layer over the first level; a fourth metal layer over the third metal layer, where the fourth metal layer is aligned to the first metal layer with less than 40 nm alignment error; and a via disposed through the first level, where the via has a diameter of less than 450 nm.