Method of fabricating a dynamic random access memory capacitor

A method for forming a capacitor coupled to a conductive region on a substrate, comprising:

• forming an insulation layer on the substrate;
• forming a barrier layer on the insulation layer;
• forming an opening penetrating through the barrier layer and the insulation to expose the conductive region;
• forming a conductive plug to fill the opening and a first polysilicon layer with a hemi-spherical grained surface on the barrier layer;
• forming a composite layer comprising a plurality of material layers formed by different materials on the hemi-spherical grained surface;
• anisotropically etching the composite layer and the polysilicon layer until exposing the barrier layer to form a substantially smooth side surface of the composite layer;
• wet etching the composite layer;
• forming a second polysilicon layer with a hemi-spherical grained surface to cover the composite layer;
• removing the composite layer;
• forming a dielectric layer to cover the first and the second polysilicon layer;
• and
• forming a top electrode layer on the dielectric layer.