Phase change RAM device and method for fabricating the same

A method for fabricating a phase change RAM device, the method comprising the steps of:

• providing a semiconductor substrate formed with an insulating interlayer including a tungsten plug;
• forming a first oxide layer on the semiconductor substrate;
• forming a pad-type bottom electrode, which makes contact with the tungsten plug, in the first oxide layer;
• forming a second oxide layer on the first oxide layer including the pad-type bottom electrode;
• forming a porous polystyrene pattern on the second oxide layer such that a predetermined portion of the second oxide layer corresponding to a center portion of the pad-type bottom electrode is covered with the porous polystyrene pattern;
• forming an oxide layer pattern exposing a peripheral portion of the pad-type bottom electrode while shielding the center portion of the pad-type bottom electrode by etching the second oxide layer using the porous polystyrene pattern;
• removing the porous polystyrene pattern;
• and
• sequentially forming a phase change layer making contact with the exposed peripheral portion of the pad-type bottom electrode and a top electrode on the second oxide layer including the oxide layer pattern and the exposed peripheral portion of the bottom electrode.