Method for forming a semiconductor device

Abstract

A method for fabricating semiconductor device is disclosed herein. The first step is to form a first oxide layer on a substrate. Subsequently formed are polycrystalline silicon layer, a polycide layer, optionally a second oxide layer, and a silicon nitride layer on the first oxide layer. A photoresist pattern on the silicon layer is formed thereafter, and the silicon nitride layer is etched using the photoresist pattern as a mask to expose a portion of the polycide layer. The photoresist pattern is then, the polycide layer is isotropically etched to form an under cut in the polycide layer under the etched nitride layer (optional second oxide layer). The width of the top portion of the isotropically etched polycide layer is smaller than the width of the etched nitride layer. The isotropically etched polycide layer is then anistropically etched, and the polycrystalline layer is etched to expose a portion of the first oxide layer to form a multi-layer structure. Finally, spacers on side-walls of the multi-layer structure are formed to create the semiconductor device, the side-wall of the anisotropicaly etched polycide layer generated after the oxidation process is prevented from penetrating the spacer of the semiconductor device according to the present invention.