Patent ID: 6268249
Filing Date: 2001-07-31
Classification: H01L

Abstract:
A method of fabricating a semiconductor device having first and second transistor regions and a field region, the method comprising the steps of:forming a first trench in the field area of a semiconductor substrate, thereby defining the first and second transistor regions;forming a second trench over the first trench in the semiconductor substrate;forming a first field oxide layer in the first trench;forming first, second, third and fourth impurity regions outside the second trench and on the bottom surface of the second trench except where the first field oxide layer is formed;forming a second field oxide layer in the second trench over the second and third impurity regions including the first field oxide layer;forming third and fourth trenches in the second field oxide layer, so as to define first and second gate oxide layers; andforming first and second gates in the third and fourth trenches.