Methods for fabricating a semiconductor device

A method for fabricating a semiconductor device, said method comprising:

• forming a gate insulating film on a semiconductor substrate;
• forming a conductive interconnection on the gate insulating film to overlap with a mask insulating film pattern comprising a nitride film;
• forming an insulating film spacer at side walls of the conductive interconnection and the mask insulating film pattern;
• forming an interlayer insulating film comprising an oxide film to planarize the surface of the resultant structure;
• forming a storage electrode contact hole and a bit line contact hole to expose the semiconductor substrate, by etching the interlayer insulating film and the oxide film according to a photolithography process using a contact mask;
• forming a contact plug to fill up the contact holes, the plug comprising silicon;
• performing a first CMP process using a basic slurry to etch the contact plug and the interlayer insulating film by a predetermined thickness;
• and
• performing a second CMP process using an acid slurry to etch the contact plug and the interlayer insulating film, thereby exposing the mask insulating film pattern;
• wherein after the first and second CMP processes the interlayer insulating film pattern has an upper surface substantially devoid of a dishing effect.