US Patent 9570550 Stacked nanowire semiconductor device

A method for forming a semiconductor device comprising forming a stack of nanowires, the stack including a first nanowire having a first length, and a second nanowire having a second length, the second nanowire arranged above the first nanowire, forming a sacrificial gate stack on the stack of nanowires, growing a source/drain region on the first, second nanowires, removing the sacrificial gate stack to expose channel regions of the first and second nanowires, and forming a gate stack over the channel regions.