Appeal No. 96-0471
Application 07/995,582
which the examiner found to be without written description
support. Since we have reversed the § 112, first paragraph,
written description rejection, it is necessary that the
combination of the admitted prior art and Tasch suggest the
base region extending to the sidewalls of the trench and
resting on top of the buffer region. We do not find such a
teaching or suggestion in Tasch. Tasch discloses that "[t]he
perimeter (i.e. sides) of the doped region extends from the
first surface to the bottom of the doped region and has a
curvature" (col. 1, lines 21-24). "The curvature is important
because the curved geometry causes electric field lines to
crowd at the perimeter. Under a high reverse bias voltage,
the electric field line crowding gives rise to an avalanche
breakdown voltage that is lower than the breakdown voltage of
the portion of the doped region with the uniform depth."
(Col. 1, lines 25-31.) Tasch solves this problem of breakdown
between a first doped region and a substrate in the substrate
by adding a second doped region extending laterally away from
the first doped region, and having dopant atoms of the same
type and less density than the dopant atoms of the first doped
region (abstract). Tasch does not disclose or suggest a
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