Steep subthreshold characteristic and enhanced transconductance of fully-recessed oxide (trench) isolated 1/4 µm width MOSFETs

This paper describes the dependence of MOSFET gate-controllability on the field isolation scheme. It is found that a fully-recessed oxide (trench) isolated MOSFET has a sharp cutoff characteristic and high transconductance in comparison with a non-recessed one. These features of the fully-recessed oxide MOSFET are due to the crowding of the gate's fringing field at the channel edge. It is also found that the gate and diffused line capacitances for the fully-recessed oxide isolation are small so that high switching speed operation can be expected.