Patent 7894237 was granted and assigned to Intel on February, 2011 by the United States Patent and Trademark Office.
A multilevel phase change memory cell may have a plurality of intermediate levels between a set and a reset or a crystalline and amorphous states. These intermediate levels between set and reset may be differentiated not only by programming current, but also by different programming pulse widths. As a result, the intermediate states may be positioned, on the programming current versus programming pulse width curve, in regions of common resistance with a relatively large range of programming current.