Appeal No. 96-0471
Application 07/995,582
claimed "buffer region" is read on N doped region 30. Since
the raised portion of the P type substrate 10 forming the
"collector region" is higher than the bottom of the N doped
region 30 forming the "buffer region," Tasch shows "a
collector region surrounded by a buffer region." Since the
curved perimeter 22 of N+ region 20 forming the "base region"
extends into the N doped region 30 forming the "buffer region"
and over the P type substrate 10 forming the "collector
region," the N+ region 20 "rests on top of the buffer region
and the collector region." The raised field oxide layers (not
numbered) shown at the sides of figure 1a extend into the
substrate and are considered analogous to "a deep trench
having at least two sidewalls and a floor." Tasch does not
show that the "base region extends to the sidewalls" (i.e., to
the field oxide) because the base region curves upward to
terminate on the surface 11.
The examiner states (EA6):
Since both Prior Art (Fig. 1) and Tasch, Jr. et al
teach a semiconductor device with a trench formed
adjacent to a PN junction, it would have been obvious to
one of ordinary skill in the art to have the lightly
doped region (P type) of Tasch, Jr. et al in Prior Art
because it lowers electric field crowding which results
[in] a high avalanche breakdown voltage. (See the
abstract of Tasch, Jr. et al).
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