Patent ID: 7585735

Claim:
A semiconductor device, comprising: a substrate having a gate dielectric layer disposed thereon; a gate electrode disposed over the gate dielectric layer, said gate electrode having first and second sidewalls; and first and second extension spacer structures disposed adjacent to said first and second sidewalls, respectively; and source and drain regions and a layer of semiconductor material selected from the group consisting of SiGe and SiGeC, said layer being disposed between said first extension spacer structure and said source region, wherein the layer of semiconductor material is not disposed between the second extension spacer structure and the drain; wherein the semiconductor device has at least one characteristic selected from the group consisting of: (a) the first and second extension spacer structures comprise first and second distinct materials; (b) the device has source/drain extensions that are asymmetrically disposed about the gate electrode; and (c) the device has a first dielectric layer disposed between the first extension spacer structure and the gate electrode, and either (i) the device has no dielectric layer disposed between the second extension spacer structure and the gate electrode, or (ii) the device has a second dielectric layer disposed between the second extension spacer structure and the gate electrode, and the first dielectric layer is substantially thicker than the second dielectric layer.