Appeal No. 1998-1069
Application No. 08/259,575
first conductivity type (n-type) (figure 6, item 19) and a
second well of a second conductivity type (p-type) (figure 6,
item 25) have exposed surfaces on a semiconductor substrate
(figure 6, item 11). These two wells are formed at implant
energies between about 150 and 400 keV (figures 1B and 1G).
An oxide layer (figure 6, item 35') is provided contiguous to
the exposed surfaces of the first and second wells, and a
first gate structure (figure 6, item 71B) and a second gate
structure (figure 6, item 71A) are provided contiguous to the
oxide layer and overlying central portions of the first and
second wells.
A first LDD implant is performed with ions of the first
conductivity type (n-) having ion kinetic energy of at least
about 70 keV and an ion dose in the range of about 5 x 10 - 512
X 10 atoms/cm (specification, page 14, lines 13-15)13 2
concurrently in the first and second wells, such that portions
of the second well that do not underlie the second gate
structure are converted to a first LDD layer of a first
conductivity type (figure 6C).
The second well and the second gate structure are then
protected from ion implantation (figure 6E). A second LDD
2
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