90 GHz f/sub T/ SiGe HFET with fully optical self-aligned sub 100 nm gate

Advanced material properties and sophisticated layer structures of SiGe hetero field-effect transistors are the basis for expected and partly demonstrated elevated RF and noise performance of these devices. However, a lack of lateral device optimization, due to lithography restrains and non self-aligned technology processes often limits the electrical performance of these transistors. Self-aligned technology concepts for hetero field-effect transistors often fail because of the incompatibility between metal gates and high temperature process steps. The new fully optical, self-aligned integration concept presented here uses a replacement-gate structure to overcome this problem.