Method of forming a MOSFET structure with planar surface

A method of forming a planar surface of a semiconductor integrated circuit, comprising the steps of:

• forming a gate oxide layer over a substrate;
• forming a polysilicon layer over said gate oxide layer;
• forming a silicon nitride layer over said polysilicon layer;
• forming and patterning a photoresist layer over said silicon nitride layer;
• etching said silicon nitride layer, polysilicon layer and gate oxide layer to form an opening, having sidewalls, exposing portions of said substrate;
• removing said photoresist layer;
• oxidizing a portion of said substrate in said opening and a portion of said conductive layer along said sidewalls in said opening;
• forming an insulating region in said opening;
• and
• forming a planar silicide layer over said insulating region and said conductive layer.

A method of forming a planar surface of a semiconductor integrated circuit;

• comprising the steps of:
• forming a conductive layer over a substrate;
• forming a silicon nitride layer over the conductive layer;
• forming and patterning a photoresist layer over the silicon nitride layer;
• etching the silicon nitride layer and conductive layer to form an opening exposing a portion of the substrate;
• removing the photoresist layer;
• oxidizing the exposed substrate and a portion of the conductive layer exposed along the sidewalls in the opening;
• forming an insulating layer over the silicon nitride layer and in the opening;
• performing an etch back of the insulating layer to expose the silicon nitride wherein an upper surface of the insulating layer is level with an upper surface of the conductive layer;
• removing the silicon nitride layer;
• and
• forming a planar silicide layer over the conductive structure.