A method of forming a dielectric layer includes the following steps. A substrate including a first area and a second area is provided. A plurality of patterns on the substrate of the first area and a blanket stacked structure on the substrate of the second area are formed. An organic dielectric layer covers the patterns, the blanket stacked structure and the substrate. The blanket stacked structure is patterned by serving the organic dielectric layer as a hard mask layer, thereby forming a plurality of stacked structures. The organic dielectric layer is removed. A dielectric layer blanketly covers the patterns, the stacked structures, and the substrate.