Quantization Effect in Capacitance Behavior of Nanoscale Silicon Multigate Mosfets

Abstract

An unusual bump in the gate capacitance characteristics of Si nanoscale MuGFETs is presented and explained here through 3D NEGF quantum simulations. The oscillations in the gate capacitance are shown to be related to the onset of occupation of subbands: due to the particular 1D density of state and through the migration of the charge centroid and quantum confinement. We also present a modeled gate capacitance that allows one to better understand the nature of the oscillation and show that it is mostly due to the variation of the 1D DOS. However, the migration of the charge centroid contributes to a few percents in the total variation of the gate capacitance. Also, the gate/oxide capacitance ratio remains low even at high gate voltage and worsen for decreasing oxide thickness.