Methods of forming phase-change memory units, and methods of manufacturing phase-change memory devices using the same

A method of forming a phase-change memory unit, comprising:

• forming a plurality of trenches in a substrate and spaced apart along a second direction, wherein each of the trenches extends along a first direction that is substantially perpendicular to the second direction;
• forming a conductive layer on the substrate and on the trenches;
• forming a first spacer layer on the conductive layer;
• selectively removing portions of the first spacer layer to form a plurality of first spacers spaced apart along the second direction, each of the plurality of first spacers extending along the first direction and partially covering the conductive layer on sidewalls and lower faces of the trenches;
• etching the conductive layer using the plurality of first spacers as an etching mask to selectively remove portions of the conductive layer from the lower faces of the trenches to form a plurality of conductive layer patterns wherein the conductive layer patterns partially expose the lower faces of the trenches;
• removing the plurality of first spacers;
• forming an insulation layer to fill up the trenches;
• planarizing the insulation layer and the conductive layer patterns until an upper surface of the substrate is exposed to form first electrodes having top surfaces that are coplanar with the upper surface of the substrate;
• forming a second spacer layer on the upper surface of the substrate, on the insulation layer, and on the top surfaces of the first electrodes;
• patterning the second spacer layer to form a second spacer that partially covers the top surfaces of the first electrodes and that exposes portions of the top surfaces of the first electrodes;
• forming a phase-change material layer on the exposed portions of the top surfaces of the first electrodes and on the second spacer;
• and
• forming a second electrode on the phase-change material layer.