Appeal No. 1999-1517
Application No. 08/837,523
The disclosed invention is directed to providing an
appropriate doping level of ions by forming a source, a drain
and a gate using a single diffusion step. The technique
provides for the normal doping of the source/drain region.
After the formation of the gate structure, side spacers are
formed beside the gate structure. After a layer of silicon
dioxide is applied to the surface of the gate structure and
the substrate, a polysilicon layer with doping ions embedded
therein is applied to the surface of the silicon oxide layer.
A heat treatment causes the doping ions embedded in the
polysilicon layer to diffuse through the silicon layer into
the substrate where the source/drain regions are formed, and
to diffuse into the gate structure, whereby the upper portion
of the gate structure becomes conducting and the gate
electrode is formed by the same heat treatment. A further
understanding of the invention can be obtained by the reading
of the following claim.
11. A method of making an IGFET, comprising the
steps of:
providing a device region of a first conductivity
type in a semiconductor substrate;
forming a gate insulator on the device region;
2
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