Semiconductor devices, and methods of fabricating the same, include forming a trench between a plurality of patterns on a substrate to be adjacent to each other, forming a first sacrificial layer in the trench, forming a first porous insulation layer having a plurality of pores on the plurality of patterns and on the first sacrificial layer, and removing the first sacrificial layer through the plurality of pores of the first porous insulation layer to form a first air gap between the plurality of patterns and under the first porous insulation layer.