A split NROM flash memory cell is comprised of source/drain regions in a
substrate. The split nitride charge storage regions are insulated from
the substrate by a first layer of oxide material and from a control gate
by a second layer of oxide material. The nitride storage regions are
isolated from each other by a depression in the control gate. In a
vertical embodiment, the split nitride storage regions are separated by
an oxide pillar. The cell is programmed by creating a positive charge on
the nitride storage regions and biasing the drain region while grounding
the source region. This creates a virtual source/drain region near the
drain region such that the hot electrons are accelerated in the narrow
pinched off region. The electrons become ballistic and are directly
injected onto the nitride storage region that is adjacent to the pinched
off channel region.