Importance of $V_{\rm th}$ and Substrate Resistance Control for RF Performance Improvement in MOSFETs

Transistor scaling with the CMOS technology advancement results in
f

_max
saturation in contrast to
fT
improvement. Effective improvement methods for such saturated
f

_max
are presented to the transistors fabricated by 45- and 65-nm low standby power CMOS technology. The primary parameters investigated are
V

_th
optimization through adjusting the channel implantation and
R

_sub
control through adjusting the active to substrate contact spacing. It is demonstrated that
V

_th
optimization and
R

_sub
control result in more than 20% and 10% improvements for
f

_max
, respectively.