A semiconductor device capable of inhibiting a conductive plug from increase of resistance or disconnection resulting from moisture discharged from a first insulator film while reducing the capacitance between adjacent first interconnection layers is obtained. This semiconductor device comprises a plurality of first interconnection layers formed on a semiconductor substrate at a prescribed interval, a first insulator film, formed to fill up the clearance between the plurality of first interconnection layers, having an opening reaching the first interconnection layers and a conductive plug charged in the opening of the first insulator film and formed to be in contact with the first interconnection layers. An impurity is selectively introduced into a first region of the first insulator film in the vicinity of contact surfaces between the first interconnection layers and the conductive plug, thereby selectively modifying the first region of the first insulator film. |