Sub-100 nm Gamma-gate MOSFET's with self-aligned drain extension formed bysolid phase diffusion

High performance 60 nm Gamma-gate n-MOSFET's have been fabricated. The very fine poly-Si gates were made using deposition and etchback of poly-Si to f orm a sidewall along the conductive poly-Si/PSG dummy stack. Due to the rel atively wide dummy stack, the low gate resistance r(g) is independent of th e actual gate length; this is especially essential for rf circuits as high gate resistance could severely degrade high frequency performance. The diff usion source, PSG layer underneath the poly-Si, allowed the formation of an ultra-shallow self-aligned drain extension by solid phase diffusion. Toget her with a steep retrograde channel using indium, good subthreshold charact eristics as well as high current drive were obtained.