A buried bit line read/program non-volatile memory cell and array is
capable of achieving high density. The cell and array is made in a
semiconductor substrate which has a plurality of spaced apart trenches,
with a planar surface between the trenches. Each trench has a side wall
and a bottom wall. Each memory cell has a floating gate for storage of
charges thereon. The cell has spaced apart source/drain regions with a
channel therebetween, with the channel having two portions. One of the
source/drain regions is in the bottom wall of the trench. The floating
gate is in the trench and is is over a first portion of the channel and
is spaced apart from the side wall of the trench. A gate electrode
controls the conduction of the channel in the second portion, which is in
the planar surface of the substrate. The other source/drain region is in
the substrate in the planar surface of the substrate. An independently
controllable control gate is also in the trench, insulated from the
floating gate and is capacitively coupled thereto. The cell programs by
hot channel electron injection, and erases by Fowler-Nordheim tunneling
of electrons from the floating gate to the gate electrode or from the
floating gate to the source/drain region at the bottom wall of the
trench. The source, drain and control gates are all substantially
parallel to one another, with the gate electrode substantially
perpendicular to the source/drain/control gates. The source/drain lines
are buried in the substrate, creating a virtual ground array.