Abstract: Provided are a semiconductor device having a self-aligned contact plug and a method of fabricating the semiconductor device. The semiconductor device includes conductive patterns, a first interlayer insulating layer, a first spacer, a second interlayer insulating layer, and a contact plug. In each conductive pattern, a conductive layer and a capping layer are sequentially deposited on an insulating layer over a semiconductor substrate. The first interlayer insulating layer fills spaces between the conductive patterns and has a height such that when the first interlayer insulating layer is placed on the insulating layer, the first interlayer insulating layer is lower than a top surface of the capping layer but higher than a top surface of the conductive layer. The first spacer surrounds the outer surface of the capping layer on the first interlayer insulating layer.