Sub-100 nm /spl Gamma/-gate MOSFETs with self-aligned drain extension formed by solid phase diffusion

High performance 60 nm /spl Gamma/-gate n-MOSFETs have been fabricated. The very fine poly-Si gates were made using deposition and etchback of poly-Si to form a sidewall along the conductive poly-Si/PSG dummy stack. Due to the relatively wide dummy stack, the low gate resistance r/sub g/ is independent of the actual gate length; this is especially essential for rf circuits as high gate resistance could severely degrade high frequency performance. The diffusion source, PSG layer underneath the poly-Si, allowed the formation of an ultra-shallow self-aligned drain extension by solid phase diffusion. Together with a steep retrograde channel using indium, good subthreshold characteristics as well as high current drive were obtained.