Gate structures with increased etch margin for self-aligned contact and the method of forming the same

Abstract

A novel gate structure and a method of forming the same for a self-aligned contact on a semiconductor substrate. The method includes forming a gate oxide layer on the semiconductor substrate. Then a first conductive layer is formed on the gate oxide layer. Next, a second conductive layer, preferably a refractory metal silicide (e.g. WSi ), is formed overlying the first conductive layer. A capping layer is formed overlying the second conductive layer. Then the capping layer is etched to form a patterned capping layer having a lower outside corner. An upper portion of the second conductive layer is selectively dry etched laterally to form a lateral recess under the capping layer to increase etch margin. A lower portion of the second conductive layer is then etched anisotropically down to the first conductive layer along a sidewall approximately vertically aligned with the lower outside corner of the patterned capping layer. The recess has an inward extant from the lower outside corner in a range of between 100-300 Angstroms. Increased etch margin is provided in the gate structure to prevent shorts between contact plugs and gate structures during contact formation.