US Patent 9257545 Stacked nanowire device with variable number of nanowire channels

A method of forming a semiconductor structure including forming a stack of layers on a top surface of a substrate, the stack of layers including alternating layers of a semiconductor material and a sacrificial material, where a bottommost layer of the stack of layers is a top semiconductor layer of the substrate, patterning a plurality of material stacks from the stack of layers, each material stack including an alternating stack of a plurality of nanowire channels and a plurality of sacrificial spacers, the plurality of nanowire channels including the semiconductor material, and the plurality of sacrificial spacers including the sacrificial material, and removing at least one of the plurality of nanowire channels from at least one of the plurality of material stacks without removing one or more of the plurality of nanowire channels from an adjacent material stack.