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.