Method for achieving very small feature size in semiconductor device by undertaking silicide sidewall growth and etching

Abstract

In the present method of fabricating a semiconductor device, initially, a semiconductor substrate is provided. An oxide layer is provided on and in contact with the substrate, and a polysilicon layer is provided on and in contact with the oxide layer. A layer of photoresist is provided on the polysilicon layer, and the photoresist is patterned to provide a photoresist body, which is used as a mask to etch away polysilicon and oxide, forming a polysilicon element thereunder. The photoresist body is then removed. A nickel layer is provided on the resulting structure, and a reaction step is undertaken to provide that nickel diffuses into the exposed top and side portions of the polysilicon body, forming nickel silicide. After the reaction step, the remaining nickel is removed, and a chemical-mechanical polishing step is undertaken to remove nickel silicide so that a pair of nickel silicide bodies remain, separated by polysilicon. Using the nickel silicide bodies as masks, the polysilicon and oxide thereunder are etched away.