Abstract
Finger STI DEMOS transistors are fabricated and its electrical characteristics is studied. The conformal mapping method, which relates the reduction of the doping concentration to the width (z o ) of the drain extension (DE) finger and the gap (z d ) between the poly plate and the DE finger is used to estimate the reduction of the doping concentration theoretically. Based on this reduced doping concentration, a breakdown voltage (BV) model is derived. The predictions of this model agree very well with the experimental data.