A method for forming a storage node contact plug in a semiconductor device is provided. The method includes: forming an inter-layer insulation layer over a substrate having a conductive plug; etching a portion of the inter-layer insulation layer using at least line type storage node contact masks as an etch mask to form a first contact hole with sloping sidewalls; etching another portion of the inter-layer insulation layer underneath the first contact hole to form a second contact hole exposing the conductive plug, the second contact hole having substantially vertical sidewalls; and filling the first and second storage node contact holes to form a storage node contact plug.