Appeal No. 2003-1365
Application No. 09/376,659
A review of Kokubu, on the other hand, reveals that the
reference relates to a semiconductor storage device having a
floating gate and a specific structure for reducing the effect of
thermal oxidation heat on uniformity of the insulating film under
the floating gate (col. 1, lines 37-40). As depicted in Figure
8, Kokubu discloses a conventional memory structure having a side
wall formed of thin thermal oxide 13–1 and thin layer of hot
thermal oxide (HTO) 13-2 which is covered by CVD oxide film 13-3
(col. 1, lines 21-29). Although Kokubu reduces the time of the
thermal oxidation of the gate oxide and prevents the formation of
the bird’s beak in the gate oxide area by using a specific
arrangement of a first oxide film, a nitride film and a second
oxide film on the side wall of a gate stack, as shown in Figures
1 and 5, it is readily apparent that the use of HTO as the second
or a subsequent side wall layer over the first layer of either
oxide or nitride is customary. The conventional memory device,
as shown in figure 8 of Kokubu, nevertheless, includes a layer of
HTO over a layer of oxide whereas the improvements offered by
Kokubu prevents the formation of the gate bird’s beak by using a
gate stack protective layer of HTO/nitride/HTO (Figure 1) or of
nitride/HTO/nitride/HTO (Figure 5).
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