A semiconductor device includes a bit line structure including a bit line contact plug and a bit line on the bit line contact plug, a storage node contact plug, an ultra low-k spacer including a gap-fill spacer contacting a side wall of the bit line contact plug and a line-type spacer contacting a side wall of the bit line, and a low-k spacer formed on the line-type spacer of the ultra low-k spacer to contact the storage node contact plug, wherein the gap-fill spacer is thicker than the line-type spacer.