Method for forming self-aligned contact hole

A method for forming a self-aligned contact hole, comprising the steps of:

• (a) providing a semiconductor substrate having a gate electrode and a diffusion region thereon, said gate electrode comprising a capping layer;
• (b) forming an oxide layer over the diffusion region and on the sidewalls of the gate electrode by thermal oxidation;
• (c) forming a conformal layer of silicon nitride overlying the substrate surface including the diffusion region and the upper surface and the sidewalls of the gate electrode;
• (d) forming an insulating layer overlying the conformal layer of silicon nitride;
• (e) etching an opening through the insulating layer self-aligned and borderless to the diffusion region by using the silicon nitride layer as an etch stop;
• and
• (e) anisotropically etching the silicon nitride layer underneath the opening, thereby exposing the diffusion region and simultaneously forming a spacer of silicon nitride on the sidewall of the gate electrode.