Method of manufacturing a phase changeable memory unit having an enhanced structure to reduce a reset current

A method of manufacturing the phase changeable memory unit comprising:

• forming a lower electrode on a substrate;
• forming an insulating interlayer structure having an opening on the lower electrode and the substrate, the opening exposing the lower electrode;
• filling the opening with a phase changeable material layer to partially cover an upper face of the insulating interlayer structure;
• and
• forming an upper electrode on the phase changeable material layer,
• wherein filling the opening with the phase changeable material layer comprises:
• forming a first phase changeable material layer having a uniform thickness along a surface of the insulating interlayer structure and a surface and a sidewall of the opening;
• planarizing the first phase changeable material layer to form a second phase changeable material layer until the upper face of the insulating interlayer structure is exposed;
• removing an upper portion of the second phase changeable material layer;
• and
• forming a third phase changeable material layer on the second phase changeable material layer.

A method of manufacturing the phase changeable memory unit comprising:

• forming a lower electrode on a substrate;
• forming an insulating interlayer structure having an opening on the lower electrode and the substrate, the opening exposing the lower electrode;
• filling the opening with a phase changeable material layer to partially cover an upper face of the insulating interlayer structure;
• and
• forming an upper electrode on the phase changeable material layer,
• wherein the opening has a width gradually decreasing downward.