Abstract
In the thesis, a CMOS compatible high-voltage STI DEMOS transistor is fabricated and its electrical characteristics studied. Two major topics are under investigated. The first topic is RESURF model. There are two RESURF sources: the p-well and the poly plate. Both the p-well and the poly plate served as a RESURF are adopted to enhance the breakdown voltage by reducing the effective doping concentration. A RESURF method, which is related to the overlap/underlap Op between the p-well and the STI, is derived for p-well. Besides, the other RESURF model, which the reduction of the doping concentration theoretically is related to the width (zo) of the drain extension finger, the gap (zd) between the poly plate and the drain extension finger, and the STI depth ys, is derived by the conformal mapping for poly plate. The second topic is a two-dimensional breakdown down model, which is adapted for both full STI DEMOS and finger-type STI DEMOS. The conformal-mapping method is used to evaluate the breakdown voltage of this two-dimensional STI DEMOS structure theoretically. A breakdown voltage model, which relates the breakdown voltage to the width of the accumulation region xa and the STI depth ys, is derived. Combined with the effective doping concentration by RESURF model, the predictions of this breakdown voltage model agree very well with the experimental data and the TCAD simulations.