Appeal No. 1997-1808 Page 5
Application No. 08/172,101
Upon a reading of the Specification as a whole, what naturally occurs to the reader is that the
inventors have further improved upon a very specific prior art semiconductor device containing a
capacitor plate composed of polysilicon (poly-Si) doped with phosphorus or arsenic. The invention is
described as an improvement over the prior art devices of Figures 4 and 5. Those prior art devices are
fabricated by forming a plate 8 “typically formed of poly-Si doped with phosphorus P or arsenic As”
and oxidizing the surface of the plate 8 “to form a first interlayer oxide film 13.” (Specification, page 6).
The plate electrode 8 within the groove, as shown in Figure 6, is also described on page 9 as being
formed of poly-Si. Then the Specification, in disclosing the invention, specifically sets forth a process of
depositing poly-Si into a groove, doping with phosphorus or arsenic to form the capacitor plate 8, and
then oxidizing the doped poly-Si to form silicon dioxide on the surface. The groove is then filled with
more poly-Si and etched to embed the poly-Si in the groove and remove excess poly-Si to provide a
planar surface for the deposition of further layers (Specification, page 19, line 22 to page 20, line 14;
Fig. 19).
At no point does the Specification indicate using materials other than poly-Si for the plate 8 and
filling layer 82. The etch stop layer is specifically disclosed as formed by thermal oxidation of the poly-
Si of the capacitor plate to form a layer of silicon dioxide. No other materials or processes are
disclosed for forming the etch stop.
We agree with Appellants that the advantage of using a silicon dioxide film on the poly-Si film 8
in order to protect the film 8 during etching of the second poly-Si film is clearly disclosed in the
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