1. A memory array comprising an array of memory cells including top electrodes having first contact surfaces extending in a first direction, bottom electrodes having second contact surfaces, and memory material elements electrically coupled to the bottom and top electrodes, the memory material elements having a generally horizontal base portion and a planar upright portion; wherein: each pair of adjacent memory cells in the array includes the memory material elements having mirror image shapes with respect to each other in the first direction; the planar upright portion of the memory material element is confined within dielectric materials on one side of the planar upright portion and on an opposite side of the planar upright portion: and each of the bottom electrodes overlies and connects to a corresponding access device of an array of access devices; wherein a horizontal memory material layer underlies and is in contact with the top electrodes, and an upper end of the upright portion of the memory material element is in contact with the horizontal memory material layer of the respective top electrode.