Appeal No. 2005-0323 Page 12
Application No. 09/577,835
we have the situation where the silicide layer 122 extends above
the top of the sidewall spacers 114 and 116. Although Gardner
takes the position (col. 3, lines 33-40) that “[t]he resulting
metal silicide 122 has a relatively low resistivity and serves as
a self-aligned contact region across source/drain regions 120 and
gate conductor 104. Absent refractory metal upon the lower
portions of the spacers, no silicide formation occurs at those
portions. Consequently, silicide bridging between gate conductor
104 and source/drain regions 120 is less likely to occur,” we
find that as taught by Mogami, because the metal silicide layer
extends above the top of the sidewall, that a short circuit can
occur. Thus, an artisan, with the teachings of Gardner and
Mogami before him/her, would be taught to extend the height of
the sidewall spacers 114 and 116 to the top of the metal silicide
layer; see for example figures 2F and 3E of Mogami.
We are not persuaded by appellants' assertion that neither
reference teaches a composite sidewall spacer at the top of the
gate stack because it is the teachings of the prior art as a
whole that must be considered. Nor are we persuaded by
appellants' assertion that there is no motivation to combine the
teachings of Gardner and Mogami because even though Gardner
discloses that the metal silicide layers result in less
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