Method for forming a transistor having silicided regions

A method for forming a metal oxide semiconductor (MOS) transistor comprising the steps of:

• providing a substrate;
• forming a conductive control electrode layer having a top surface;
• forming a dielectric layer overlying the conductive control electrode layer, the dielectric layer being a nitride material;
• etching the dielectric layer and the conductive control electrode layer to form a control electrode overlying the substrate, the dielectric layer forming a masking layer over a top portion of the conductive control electrode layer;
• forming a source region and a drain region within the substrate;
• forming an oxide sidewall spacer laterally adjacent the conductive control electrode;
• forming a first silicided region over the source and the drain regions, the first silicided regions being cobalt silicide;
• removing the masking layer selective to the oxide sidewall spacer wherein a top portion of the oxide sidewall spacer extends above the top surface of the conductive control electrode;
• and
• forming a second silicided region over the control electrode, the second silicide region being titanium silicide.

A method for forming a transistor comprising the steps of:

• providing a substrate;
• forming a control electrode overlying the substrate, the control electrode having a top portion which functions as a masking layer which prevents silicidation of the control electrode, the top portion which functions as a masking layer being a nitride dielectric material;
• forming a source region and a drain region within the substrate and adjacent the control electrode;
• forming an oxide sidewall spacer laterally adjacent the control electrode;
• forming a first metal layer overlying the source region and the drain region;
• forming a first silicided region by heating the first metal layer, the heating reacting the first metal layer with the source region an the drain region to form cobalt silicide which allows for the formation of shallow source and drain regions;
• removing the top portion of the control electrode which functions as a masking layer selective to the oxide sidewall spacer wherein a portion of the oxide sidewall spacer extends above the control electrode due to the selectivity of the step of removing;
• forming a second metal layer overlying the control electrode;
• and
• forming the second silicided region, which is different form the first silicided region, by heating the second metal layer, the heating reacting the second metal layer with the control electrode to form titanium silicide which reduces lateral doping diffusion of dopant atoms in the control electrode.