Methods of fabricating phase change memory cells having a cell diode and a bottom electrode self-aligned with each other

A method of forming an integrated circuit device including a vertical diode, the method comprising:

• forming an insulating layer on an integrated circuit substrate;
• forming a sacrificial layer on the insulating layer;
• forming a cell contact hole penetrating the sacrificial layer and the insulating layer;
• forming a vertical cell diode in a lower region of the cell contact hole;
• forming a preliminary bottom electrode filling the cell contact hole;
• removing the sacrificial layer without removing the preliminary bottom electrode to provide a protruding portion of the preliminary bottom electrode;
• and
• planarizing the protruding portion of the preliminary bottom electrode form a bottom electrode in the cell contact hole having a top surface that is located at a substantially same level as a top surface of the lower insulating layer.