Method of forming semiconductor device having self-aligned plug

A method of fabricating a semiconductor device, comprising:

• forming a conductive pattern on a substrate;
• forming an insulating layer on the conductive pattern and having an opening exposing the conductive pattern;
• forming a bottom electrode on the conductive pattern and a first sidewall of the opening;
• forming a spacer on the bottom electrode and a second sidewall of the opening, the spacer and the bottom electrode being formed to be lower than a top surface of the insulating layer;
• forming a data storage plug on the bottom electrode and the spacer, the data storage plug having a first sidewall aligned with a sidewall of the bottom electrode and a second sidewall aligned with a sidewall of the spacer;
• and
• forming a bit line on the data storage plug.