A virtual ground memory array (VGA) is formed by a storage layer over a
substrate with a conductive layer over the storage layer. The conductive
layer is opened according to a patterned photoresist layer. The openings
are implanted to form source/drain lines in the substrate, then filled
with a layer of dielectric material. Chemical mechanical polishing (CMP)
is then performed until the top of the conductive layer is exposed. This
leaves dielectric spacers over the source/drain lines and conductive
material between the dielectric spacers. Word lines are then formed over
the conductive material and the dielectric spacers. As an alternative,
instead of using a conductive layer, a sacrificial layer is used that is
removed after the CMP step. After removing the sacrificial portions, the
word lines are formed. In both cases, dielectric spacers reduce
gate/drain capacitance and the distance from substrate to gate is held
constant across the channel.