A bi-directional read/program non-volatile memory cell and array is
capable of achieving high density. Each memory cell has two spaced
floating gates for storage of charges thereon. The cell has spaced apart
source/drain regions with a channel therebetween, with the channel having
three portions. One of the floating gate is over a first portion; another
floating gate is over a second portion, and a gate electrode controls the
conduction of the channel in the third portion between the first and
second portions. A control gate is connected to each of the source/drain
regions, and is also capacitively coupled to the floating gate. The cell
programs by hot channel electron injection, and erases by Fowler-Nordheim
tunneling of electrons from the floating gate to the gate electrode.
Bi-directional read permits the cell to be programmed to store bits, with
one bit in each floating gate. An array of such memory cells comprises
rows of cells in active regions adjacent to one another separated from
one another by the semiconductive substrate material without any
isolation material. Cells in the same column have the source/drain region
in common, the drain/source region in common and a first and second
control gates in each of the trenches in common. Cells in adjacent
columns have the source/drain in common and the first control gate in
common.