Semiconductor device having a reduced leakage current and a fabrication process thereof

1. A method of fabricating a semiconductor memory device, comprising the steps of:

forming a gate electrode on a substrate;

forming first and second diffusion regions in said substrate respectively adjacent to first and second side walls of said gate electrode;

forming first and second side wall insulation films respectively on said first and second side walls of said gate electrode;

forming a first interlayer insulation film on said gate electrode such that said first interlayer insulation film covers said first and second side wall insulation films;

forming a first contact hole in said first interlayer insulation film such that said first contact hole exposes said first diffusion region;

forming a bit line pattern on said first interlayer insulation film so as to fill said first contact hole in electrical contact with said first diffusion region;

forming a second interlayer insulation film on said first interlayer insulation film so as to cover said bit line pattern;

forming a second contact hole in said second interlayer insulation film such that said second contact hole penetrates through said first interlayer insulation film and exposes said second diffusion region;

forming an accumulation electrode of a memory cell capacitor such that said accumulation electrode fills said second contact hole and contacts said second diffusion region;

forming a capacitor dielectric film on said accumulation electrode; and

forming an opposing electrode on said capacitor dielectric film,

wherein said step of forming said first and second side wall insulation films includes the steps of:

depositing a first insulation film on said gate electrode such that said first insulation film covers said first and second side walls of said gate electrode;

applying a first anisotropic etching process proceeding generally perpendicularly to a principal surface of said substrate, to said first insulation film to form first and second lower side wall insulation films, respectively, on said first and second side walls of said gate electrode in an intimate contact therewith;

depositing a second insulation film on said gate electrode such that said second insulation film covers said first and second lower side wall insulation films; and

applying a second anisotropic etching process proceeding generally perpendicularly to said principal surface of said substrate, to said second insulation film to form first and second upper side wall insulation films, respectively, on said first and second lower side wall insulation films.

2. The method as claimed in claim 1 , comprising, after said step of forming said first contact hole but before said step of forming said bit line pattern, of applying a dry etching process to an exposed surface of said first diffusion region for removal of an oxide film therefrom.

3. The method as claimed in claim 1 , further comprising, after said step of forming said second contact hole but before said step of forming said accumulation electrode, of applying a dry etching process to an exposed surface of said second diffusion region for removal of an oxide film therefrom.

4. The method as claimed in claim 1 , further comprising, after said step of forming said first contact hole but before said step of forming said bit line pattern, of applying a dry etching process to an exposed surface of said first diffusion region.

5. The method as claimed in claim 1 , further comprising, after said step of forming said second contact hole but before said step of forming said accumulation electrode, of applying a dry etching process to an exposed surface of said second diffusion region.

6. A method of fabricating a semiconductor memory device, comprising the steps of:

forming a gate electrode on a substrate;

forming first and second diffusion regions in said substrate respectively adjacent to first and second side walls of said gate electrode;

forming first and second side wall insulation films respectively on said first and second side walls of said gate electrode;

forming a first interlayer insulation film on said gate electrode such that said first interlayer insulation film covers said first and second side wall insulation films;

forming a first contact hole in said first interlayer insulation film such that said first contact hole exposes said first diffusion region;

forming a bit line pattern on said first interlayer insulation film so as to fill said first contact hole in electrical contact with said first diffusion region;

forming a second interlayer insulation film on said first interlayer insulation film so as to cover said bit line pattern;

forming a second contact hole in said second interlayer insulation film such that said second contact hole penetrates through said first interlayer insulation film and exposes said second diffusion region;

forming an accumulation electrode of a memory cell capacitor such that said accumulation electrode fills said second contact hole and contacts said second diffusion region;

forming a capacitor dielectric film on said accumulation electrode; and

forming an opposing electrode on said capacitor dielectric film,

wherein said step of forming said first and second side wall insulation films includes the steps of:

depositing a first insulation film on said gate electrode such that said first insulation film covers said first and second side walls of said gate electrode;

applying a first anisotropic etching process to said first insulation film to form first and second side wall insulation films, respectively, on said first and second side walls of said gate electrode in an intimate contact therewith;

doping said first and second side wall insulation films with N;

depositing a second insulation film on said gate electrode such that said second insulation film covers said first and second side wall insulation films; and

applying a second anisotropic etching process to said second insulation film to form first and second upper side wall insulation films, respectively, on said first and second side wall insulation films.