A method for forming a raised source and drain structure without using selective
epitaxial silicon growth. A
semiconductor substrate is provided having one or more gate areas covered by
dielectric structures. Doped polysilicon structures are adjacent to the
dielectric structures on each side and are co-planar with the
dielectric structures from a CMP process. The first dielectric structures are removed to form gate openings and a liner
oxide layer is formed on the bottom and sidewalls of the gate openings.
Dielectric spacers are formed on the liner
oxide layer over the sidewalls of the gate openings, and the liner
oxide layer is removed from the bottom of the gate openings and from over the doped polysilicon structures. Source and drain regions are formed in the
semiconductor substrate by diffusing
impurity ions from the doped polysilicon layer. A
gate oxide layer and a gate polysilicon layer are formed over the
semiconductor structure and the gate polysilicon layer is planarized to form a gate
electrode. In a key step, the dielectric spacers are removed to form spacer openings, and
impurity ions are implanted through the spacer openings and annealed to form source and drain extensions. The dielectric spacers are reformed and a self-aligned
silicide layer is formed on the doped polysilicon structure and the gate
electrode. Alternatively, the self-aligned
silicide layer can be formed prior to removing the dielectric spacers and implanting ions to form source and drain extensions.