Method of forming fully silicided NMOS and PMOS semiconductor devices having independent polysilicon gate thicknesses, and related device

A method comprising:

• forming an NMOS gate over a semiconductor substrate, the NMOS gate having a first thickness;
• forming a PMOS gate over the semiconductor substrate, the PMOS gate having a second thickness different than the first thickness and the PMOS gate being undoped;
• forming spacers on sidewalls of the NMOS gate having the first thickness and sidewalls of the PMOS gate having the second thickness, the spacers being formed simultaneously;
• forming source and drain regions adjacent to the spacers, the source and drain regions containing no silicide layer;
• forming a conformal cover layer over the semiconductor substrate;
• removing the conformal cover layer over the NMOS gate and the PMOS gate;
• performing a simultaneous silicidation of the NMOS gate and the PMOS gate after the step of forming the source and drain regions containing no silicide layer, the source and drain regions containing no silicide layer being protected by the conformal cover layer from the simultaneous silicidation of the NMOS gate and the PMOS gate;
• removing remaining portions of the conformal cover layer;
• and
• performing a simultaneous silicidation of all the source and drain regions after the step of removing remaining portions of the conformal cover layer;
• wherein each of the forming the NMOS gate and forming the PMOS gate further comprises:
• forming a first polysilicon layer over the semiconductor substrate;
• forming an oxide layer over the first polysilicon layer;
• removing the oxide layer over the first polysilicon layer of the NMOS gate;
• and
• forming a second polysilicon layer over the oxide layer.