A method of fabricating a semiconductor device includes forming a buffer insulating film over a semiconductor substrate including a conductive pattern. The buffer insulating film is etched using a storage node mask to form a buffer insulating pattern exposing the conductive pattern. The buffer insulating pattern defines a region wider than a storage node region. An etch stop film is formed over the conductive pattern and the buffer insulating pattern. An interlayer insulating film is formed over the etch stop film. The interlayer insulating film is etched using the storage node mask to expose the etch stop film. The exposed etch stop film is etched to form the storage node region exposing conductive pattern. A lower storage node is formed over the storage node region.