An integrated circuit (IC) device includes a line structure including a conductive line formed on a substrate and an insulation capping pattern that covers the conductive line; an insulation spacer covering a sidewall of the line structure; a conductive plug spaced apart from the conductive line in a first horizontal direction with the insulation spacer between the conductive plug and the conductive line; a conductive landing pad arranged on the conductive plug to vertically overlap the conductive plug; and a capping layer including a first portion between the conductive landing pad and the insulation capping pattern, wherein the first portion of the capping layer has a shape in which a width in the first horizontal direction gradually increases as a distance from the substrate increases between the conductive landing pad and the insulation capping pattern.