Appeal No. 1997-3162
Application 08/540,961
isolation is "better" than LOCOS isolation, is not considered
determinative. Something may be obvious even if has
disadvantages. What is important is whether one of ordinary
skill in the art would have sought to use the widened gate
structure of Kikuchi if the surrounding LOCOS isolation was
replaced with shallow trench isolation. The Examiner's bare
conclusion that it would have been obvious to mechanically
substitute trench isolation for the LOCOS isolation fails to
address whether the problems solved by Kikuchi would have
existed with trench isolation and, therefore, would have
suggested applying Kikuchi's solution.
Trench isolation is produced by etching (Shimizu, col. 2,
lines 40-45) and, thus, would not produce the oxidation
stresses of LOCOS leading to the first problem described in
Kikuchi (translation, page 3). Trench isolation has a planar
surface (Shimizu, col. 2, lines 55-59; figure 3E) and, thus,
would not produce overexposure of the ends of the gate due to
the height difference of the LOCOS isolation above the active
region leading to the second problem described in Kikuchi
(translation, page 3). Accordingly, we do not find any
evidence why one of ordinary skill in the art would have been
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