A non-volatile memory cell structure that is capable of holding two data
bits. The structure includes a trench in a substrate with two sides of
the trench being lined with a trapping material. The trench is filled
with an oxide dielectric material and a control gate is formed over the
oxide-filled trench. Source/drain regions are adjacent the trench sides
with the trapping material. An energy barrier between the drain and
source regions has two local high points that correspond to the trench
corners. To read the device, sufficient gate voltage is applied to invert
the channel and a sufficient drain voltage is applied to pull down the
drain-side barrier. If charges of opposite polarity are trapped in the
source-side trench corner, the source barrier will be significantly
lowered so that current flows between source and drain under read
conditions.