METHOD FOR FORMING THE ISOLATION LAYER OF SEMICONDUCTOR DEVICE

摘要

A method for fabricating an isolation layer in a semiconductor device is provided to avoid generation of a moat by rounding the corner of an interface between an active region and an isolation region and by preventing a gap-fill oxide layer from being lost. A pad oxide layer(110) and a pad nitride layer are sequentially stacked on a silicon substrate(100) to form a pad pattern for defining an isolation region. A predetermined depth of the silicon substrate is etched to form a trench by using the pad pattern as an etch mask. A part of the pad oxide layer exposed through the trench is removed by a first blanket etch-back process using an HF solution as an etch solution. The pad nitride layer is removed by a second blanket etch-back process using an H3PO4 solution as an etch solution to expose a part of the end part of the pad oxide layer remaining after the first blanket etch-back process. The upper corner of the trench exposed through the residual pad oxide layer is rounded by a light etch process. A rounding oxide process is performed on the resultant structure to form a round oxide layer(140) on the inner wall of the trench. A gap-fill oxide layer(150) is filled in the trench having the round oxide layer.