A method for manufacturing a semiconductor device includes forming a first pattern structure having a first opening on a lower structure comprising a semiconductor substrate. The first pattern structure includes a stacked pattern and a first spacer layer covering at least a side surface of the stacked pattern. A first flowable material layer including a SiOCH material is formed on the first spacer layer to fill the first opening and cover an upper portion of the first pattern structure. A first curing process including supplying a gaseous ammonia catalyst into the first flowable material layer is performed on the first flowable material layer to form a first cured material layer that includes water. A second curing process is performed on the first cured material layer to form a first low-k dielectric material layer. The first low-k dielectric material layer is planarized to form a planarized first low-k dielectric material layer.