Non-volatile memory cells store a level of charge corresponding to the
data being stored in a dielectric material storage element that is
sandwiched between a control gate and the semiconductor substrate surface
over channel regions of the memory cells. More than two memory states are
provided by one of more than two levels of charge being stored in a
common region of the dielectric material. More than one such common
region may be included in each cell. In one form, two such regions are
provided adjacent source and drain diffusions in a cell that also
includes a select transistor positioned between them. In another form,
NAND arrays of strings of memory cells store charge in regions of a
dielectric layer sandwiched between word lines and the semiconductor
substrate.