Patent ID: 6025237
Filing Date: 2000-02-15
Classification: H01L

Abstract:
A method of forming a field effect transistor, comprising the steps of:implanting first conductivity type dopants at a first dose level into a first portion of a drift region of first conductivity type semiconductor;oxidizing the first portion of the semiconductor drift region to form a field oxide isolation region and simultaneously form a drain region extension of first conductivity type semiconductor by driving the dopants implanted at the first dose level into the drift region;forming a body region of second conductivity type semiconductor in a second portion of the semiconductor drift region, spaced from the first portion;forming a gate electrode extending opposite the body region and field oxide isolation region; andforming source and drain regions of first conductivity type semiconductor in the body region and in a third portion of the drift region spaced from the second portion, respectively, by implanting first conductivity type dopants at a second dose level which is greater than the first dose level using the gate electrode and field oxide isolation region as an implant mask;wherein said step of implanting first conductivity type dopants at a first dose level is preceded by the step of forming a gate oxide layer on a surface of the drift region; wherein said step of forming a body region is preceded by the step of forming a gate conductive layer having an opening therein that extends opposite the second portion of the drift region, on the gate oxide layer and field oxide isolation region; and wherein said step of forming a body region comprises implanting dopants of second conductivity type at a third dose level into the drift region using the gate conductive layer as an implant mask.