A method for forming a
CMOS device in a manner so as to avoid
dielectric layer
undercut during a pre-
silicide cleaning step is described. During formation of
CMOS device comprising a
gate stack on a
semiconductor substrate surface, the patterned
gate stack including
gate dielectric below a conductor with vertical sidewalls, a
dielectric layer is formed thereover and over the substrate surfaces. Respective
nitride spacer elements overlying the
dielectric layer are formed at each vertical sidewall. The
dielectric layer on the
substrate surface is removed using an etch process such that a portion of the
dielectric layer underlying each spacer remains. Then, a
nitride layer is deposited over the entire sample (the
gate stack, the spacer elements at each gate sidewall, and substrate surfaces) and subsequently removed by an etch process such that only a portion of said
nitride film (the “plug”) remains. The plug seals and encapsulates the
dielectric layer underlying each said spacer, thus preventing the dielectric material from being
undercut during the subsequent pre-
silicide clean process. By preventing
undercut, this invention also prevents the etch-stop film (deposited prior to
contact formation) from coming into contact with the
gate oxide. Thus, the integration of thin-spacer
transistor geometries, which are required for improving
transistor drive current, is enabled.