The present disclosure describes semiconductor devices and methods of fabricating the same. The method includes forming an interlayer insulating layer on a substrate and forming conductive patterns in the interlayer insulating layer. A pore density of an upper portion of the interlayer insulating layer is higher than that of a lower portion of the interlayer insulating layer, and a pore density of an intermediate portion of the interlayer insulating layer gradually increases toward the upper portion of the interlayer insulating layer. An air gap is provided between the conductive patterns.