Numerical treatment of nonrectangular field-oxide for 3-D MOSFET simulation

A simulation method that takes into account effects at the channel edge due to nonplanar interfaces is introduced. The authors applied the box integration method after Forsythe (1960) for discretization. The most important nonplanar interface occurs at the transition of the gate oxide to the field oxide, which is commonly called bird´s beak. Approximating this interface with right angles leads to unrealistic results. The authors introduce the numerical treatment in three-dimensional MOSFET simulation with nonplanar interfaces. The physical model used is presented, and the numerical implementation of the basic equations is shown. The simulations have been carried out with MINIMOS 5 a fully three-dimensional simulation program. Three-dimensional effects such as threshold shift for small-channel devices, channel narrowing, and the enhanced conductivity at the channel edge have been successfully modeled