A semiconductor device includes a semiconductor substrate including a first region and a second region, first metal lines spaced apart from each other at a first interval on the first region, second metal lines spaced apart from each other at a second interval on the second region, the second interval being less than the first interval, and a passivation layer on the semiconductor substrate and covering the first and second metal lines, the passivation layer including sidewall parts covering sidewalls of the first metal lines and the second metal lines, the sidewall parts including a porous dielectric layer, upper parts covering top surfaces of the first metal lines and the second metal lines, and an air gap defined by the sidewall parts between the second metal lines.