Semicoductor devices with germanium-rich active layers & doped transition layers

Semiconductor device comprising a plurality of germanium rich nanowires 508 aligned vertically over a silicon substrate 504. A silicon germanium transition layer 507C is disposed between the Ge nanowires and the Si substrate. A p-type delta-doped SiGe layer 507B is disposed below the SiGE transition layer and an n-type doped layer 507A between the δ-doped layer and substrate. A gate stack is disposed over the nanowires completely surrounding a length of each of the nanowires. Spacers 516 are disposed at the end of the gate stack and source and drain regions 514 are disposed on opposite sides of the gate stack and in contact with the plurality of nanowires. The nanowires may be vertically separated by an intervening sacrificial semiconductor layer, wherein the first nanowire is deposited on a first sacrificial layer which is disposed directly on the transition layer. The transition layer may be intrinsic whilst the delta doped layer is doped with boron and the n-type doped layer is doped ...