In a method of manufacturing an MRAM device, a first sacrificial layer, an etch stop layer, and a second sacrificial layer are sequentially formed on a substrate and then partially etched to form openings therethrough. Lower electrodes are formed to fill the openings. The first and second sacrificial layers and portions of the etch stop layer are removed to form etch stop layer patterns surrounding upper portions of sidewalls of the lower electrodes, respectively. An upper insulating layer pattern is formed between the etch stop layer patterns to partially define an air pad between the lower electrodes. A first magnetic layer, a tunnel barrier layer, a second magnetic layer, and an upper electrode layer are formed, and are etched to form a plurality of magnetic tunnel junction (MTJ) structures. Each MTJ structure includes a sequentially stacked first magnetic layer pattern, tunnel layer pattern, and second magnetic layer pattern, and each of the MTJ structures contacts a corresponding one of the lower electrodes.