A method for fabricating a semiconductor device includes: forming a first conductive structure over a substrate; forming a multi-layer spacer including a non-conformal sacrificial spacer on both sidewalls of the first conductive structure; forming a second conductive structure adjacent to the first conductive structure with the multi-layer spacer therebetween; forming an air gap by removing the non-conformal sacrificial spacer; forming a capping layer covering the second conductive structure and the air gap; forming an opening that exposes a top surface of the second conductive structure by etching the capping layer; and forming a conductive pad coupled to the second conductive structure in the opening.