Method for forming a field oxide layer of a semiconductor integrated

Abstract

A method for forming a field oxide layer of a highly integrated semiconductor device comprises the steps of depositing a pad oxide layer and a nitride layer over a substrate, removing the nitride layer over a field region, forming spacers on the side walls of the remaining nitride layer, doping an impurity into the field region using the spacers as a mask, thermally oxidizing the substrate exposed in the field region, growing the field oxide layer, and planarizing the upper portion of the field oxide layer by an etchback process, thereby reducing the step coverage problem of the field oxide layer. Therefore, the size of bird's beak and stress can be reduced at the edges of the field region. The heavily doped channel stop layer is formed only in the middle section of the field region, thereby preventing the lowering of the breakdown voltage and punch-through.