Appeal No. 2001-2659
Application 08/919,674
Claim 1 is illustrative:
1. A method for manufacturing a nonvolatile semiconductor
storage device comprising the steps of:
forming an element separating oxide layer onto a
semiconductor base for defining a first region for forming a
nonvolatile memory cell and a second region for forming an MOS
transistor for use in a peripheral circuit;
forming a first gate insulating layer on said first and
second regions of a surface of said semiconductor base;
forming a first polysilicon layer over the entire surface of
said semiconductor base, and then patterning said first
polysilicon layer in a manner such that said first polysilicon
layer is left covering only said first gate insulating layer of
said first region;
sequentially forming a second gate insulating layer having
three insulating layers and a second polysilicon layer over the
entire surface of said first region and said second region;
sequentially removing said second polysilicon layer, said
second gate insulating layer and said first gate insulating
layer, respectively, in said second region;
forming a third gate oxide layer over a surface of said
semiconductor base corresponding to said second region by means
of thermal oxidation;
coating a third polysilicon layer over the entire surface of
said first region and said second region, and patterning said
third polysilicon layer to form a gate electrode over said second
region; and
patterning said second polysilicon layer, said second gate
insulating layer, and said first polysilicon layer to form a gate
electrode in said first region wherein a control gate is formed
by patterning said second polysilicon layer, said second gate
insulating layer and said first polysilicon layer, and a floating
gate is formed by patterning said first polysilicon layer.
2
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