a multilevel phase change memory may be formed of a chalcogenide material formed between a pair of spaced electrodes . the cross - sectional area of the chalcogenide material may decrease as the material extends from one electrode to another . as a result , the current density decreases from one electrode to the other . this means that a higher current is necessary to convert the material that has the largest cross - sectional area . as a result , different current levels may be utilized to convert different amounts of the chalcogenide material to the amorphous or reset state . a distinguishable resistance may be associated with each of those different amounts of amorphous material , providing the opportunity to engineer a number of different current selectable programmable states .