Method for forming self-aligned contact in semiconductor device

Abstract

A method for forming a self-aligned contact on a semiconductor substrate provided with a plurality of field-effect transistors. The method comprises the steps of: forming a thin nitride insulating layer on a gate structure and a diffusion region of the transistor; forming a first insulating layer, which is then planarized to expose the nitride insulating layer on the gate structure; etching through the first insulating layer to form a first part of a contact hole; forming a first part of a contact in said first part of the contact hole; forming a second insulating layer; etching through the second insulating layer to form a second part of the contact hole; and forming a second part of the contact in the second part of the contact hole. The two-stage etching process for forming a conductive contact effectively prevents over-etching and short-circuiting between a wordline and a bitline.