In a semiconductor device having an insulating layer structure and method of manufacturing the same, a substrate including a first region and a second region may be provided. A first pattern structure may be formed on the first region of the substrate. A second pattern structure may be formed on the second region of the substrate, and have a height that is greater than the height of the first pattern structure. An insulating layer structure is formed on the first and second pattern structures and includes a protrusion near an area at which the first and second regions meet each other. An upper surface of the insulating interlayer structure is higher than a top surface of the second pattern structure. The protrusion may have at least one side surface having a staircase shape. A planarized insulating interlayer may be formed without substantial damage to the infrastructure by using the insulating layer structure in accordance with example embodiments.