In a method of manufacturing an MRAM device, a memory unit including a lower electrode, an MTJ structure and an upper electrode sequentially stacked is formed on a substrate. A protective layer structure including a capping layer, a sacrificial layer and an etch stop layer sequentially stacked is formed on the substrate to cover the memory unit. An insulating interlayer is formed on the protective layer structure. The insulating interlayer is formed to form an opening exposing the protective layer structure. The exposed protective layer structure is partially removed to expose the upper electrode. A wiring is formed on the exposed upper electrode to fill the opening.