Appeal No. 1998-2918
Application No. 08/508,874
With these guidelines in mind, we consider the scope of the claims to be
indeterminate. In light of the disclosure, and with reference numerals as shown in the
drawings, claim 1 recites the step (emphasis added) of "providing a semiconductor
substrate having a buried region of silicon dioxide (12) below a major surface (14) and a
silicon layer (13) below the major surface (14) and above the buried region of silicon
dioxide (12), wherein the silicon layer (13) has an edge...."
The claim later recites (emphasis added), "oxidizing the semiconductor substrate
to form an isolation structure (22), a portion of the isolation structure (22) protrudes
above the major surface (14) of the semiconductor substrate and is overlying the edge
of the silicon layer (13)...."
The "edge" of the silicon layer that a portion of the isolation structure overlies is
described in the specification. "Bird's head region 21 provides a silicon oxide
layer...above the edge of active area 13 which will improve the control of the threshold
voltage along the edge of active area 13." (Specification, page 7, li. 22-27.)
The "edge" is formed during the oxidation step, according to page 7 of the
specification.
FIG. 3 illustrates an enlarged cross-sectional view of isolation
structure 22 after oxidation. The oxidation consumes silicon layer 13
under the exposed portions of etchant barrier layer 16. In this
embodiment, silicon layer 13 is converted to silicon dioxide and combines
with etchant barrier layer 16 and buried isolation region 12 both of which
are made of silicon dioxide. The combination of these three layers forms
a single region of silicon dioxide such that isolation structure 22 will grow
to be...above surface 14.
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