Memory devices and methods of forming memory devices including forming a plurality of preliminary electrodes, each of the plurality of preliminary electrodes including a protruding region, protruding from a first mold insulating layer, forming a second mold insulating layer on the first mold insulating layer, removing at least a portion of the plurality of preliminary electrodes to form a plurality of openings in the second mold insulating layer and a plurality of lower electrodes, and forming a plurality of memory elements in the plurality of openings. Memory devices and methods of forming memory devices including forming one or more insulating layers on sidewalls of all or part of a plurality of lower electrodes and/or a plurality of memory elements.