Semiconductor device with air gap and method for fabricating the same

A semiconductor device, comprising:

• a plurality of bit line structures formed to be spaced apart from each other over a semiconductor substrate;
• a bit line spacer formed on both sidewalls of each of the bit line structures;
• a plurality of storage node contact plugs that are formed between the bit line structures and contact the semiconductor substrate;
• a pair of line-shaped air gaps that is formed between the bit line structures and the storage node contact plugs and parallel to both sidewalls of the bit line structure;
• a capping layer that caps the line-shaped air gaps and expose the top surfaces of the storage node contact plugs;
• and
• a conductive pad coupled to the storage node contact plugs,
• wherein the pair of the line-shaped air gaps includes a lower air gap that is adjacent a sidewall of a lower portion of each of the bit line structures and an upper air gap that is adjacent to a sidewall of an upper portion of each of the bit line structures, and the upper air gap has a narrower width than the lower air gap, and
• wherein the capping layer include extension portions for partially filling an upper portion of each of the upper air gaps.