US Patent 7138681 High density stepped, non-planar nitride read only memory

A non-planar, stepped NROM array is comprised of cells formed in trenches and on pillars that are etched into a substrate. Each cell has a plurality of charge storage regions in its nitride layer and a pair of source/drain regions that are shared with adjacent cells in a column. The source/drain regions, formed in the pillar/trench sidewalls, couple the column cells serially into bitlines. The rows of the array are each coupled by a wordline. A second set of trenches separates the columns of cells.