A method for fabricating a semiconductor device, comprising: forming a first composite structure including a core region and an edge region around the core region, on a substrate, wherein the first composite structure includes a plurality of laminated layers of first composite layers; forming a second composite structure on a first surface portion of the core region of the first composite structure, wherein the second composite structure includes a plurality of laminated layers of second composite layers; forming a first mask layer, covering a sidewall of the second composite structure and a second surface portion of the core region outside of an outer peripheral of the second composite structure, exposing at least a portion of the edge region of the first composite structure and not covering the top surface of the second composite structure; forming a second mask layer, on a surface portion of the second composite structure and spaced apart from the first mask layer by a first annular opening; and etching a top first layer of the first composite layers in the edge region and a top first layer of the second composite layers at a bottom of the first annular opening, using the first mask layer and the second mask layer as an etch mask, wherein both the number of layers of the first composite layers and the number of layers of the second composite layers are three and more, the method further including: performing a first-step etching after etching the top first layer of the first composite layers in the edge region and the top first layer of the second composite layers at the bottom of the first annular opening, wherein the first-step etching includes: etching a sidewall of the first mask layer and a sidewall of the second mask layer to expose a surface portion of the top first layer of the second composite layers outside of an outer peripheral of the second mask layer and a surface portion of the top first layer of the first composite layers outside of an outer peripheral of the first mask layer, and repeatedly etching the exposed first composite layers and the second composite layers, using the etched first mask layer and the second mask layer as an etch mask to form the number of layers of the first composite layers and the number of layers of the second composite layers. forming a first composite structure including a core region and an edge region around the core region, on a substrate, wherein the first composite structure includes a plurality of laminated layers of first composite layers; forming a second composite structure on a first surface portion of the core region of the first composite structure, wherein the second composite structure includes a plurality of laminated layers of second composite layers; forming a first mask layer, covering a sidewall of the second composite structure and a second surface portion of the core region outside of an outer peripheral of the second composite structure, exposing at least a portion of the edge region of the first composite structure and not covering the top surface of the second composite structure; forming a second mask layer, on a surface portion of the second composite structure and spaced apart from the first mask layer by a first annular opening; and etching a top first layer of the first composite layers in the edge region and a top first layer of the second composite layers at a bottom of the first annular opening, using the first mask layer and the second mask layer as an etch mask, wherein both the number of layers of the first composite layers and the number of layers of the second composite layers are three and more, the method further including: performing a first-step etching after etching the top first layer of the first composite layers in the edge region and the top first layer of the second composite layers at the bottom of the first annular opening, wherein the first-step etching includes: etching a sidewall of the first mask layer and a sidewall of the second mask layer to expose a surface portion of the top first layer of the second composite layers outside of an outer peripheral of the second mask layer and a surface portion of the top first layer of the first composite layers outside of an outer peripheral of the first mask layer, and repeatedly etching the exposed first composite layers and the second composite layers, using the etched first mask layer and the second mask layer as an etch mask to form the number of layers of the first composite layers and the number of layers of the second composite layers. etching a sidewall of the first mask layer and a sidewall of the second mask layer to expose a surface portion of the top first layer of the second composite layers outside of an outer peripheral of the second mask layer and a surface portion of the top first layer of the first composite layers outside of an outer peripheral of the first mask layer, and repeatedly etching the exposed first composite layers and the second composite layers, using the etched first mask layer and the second mask layer as an etch mask to form the number of layers of the first composite layers and the number of layers of the second composite layers.