A method of fabricating a semiconductor device includes forming switching devices on a substrate. A lower structure is formed in the substrate having the switching devices. A lower conductive layer is formed on the lower structure. Sacrificial mask patterns are formed on the lower conductive layer. Lower conductive patterns are formed by etching the lower conductive layer using the sacrificial mask patterns as an etch mask. An interlayer insulating layer is formed on the substrate having the lower conductive patterns. Interlayer insulating patterns are formed by planarizing the interlayer insulating layer until the sacrificial mask patterns are exposed. Openings exposing the lower conductive patterns are formed by removing the exposed sacrificial mask patterns. Upper conductive patterns self-aligned with the lower conductive patterns are formed in the openings.