SEMICONDUCTOR DEVICE AND FABRICATION METHOD THEREOF

A semiconductor device and a method for fabricating the semiconductor device are provided. The method includes forming a first composite structure, including a plurality of first composite layers, on a substrate, and forming a second composite structure, including a plurality of second composite layers on a surface portion of the first composite structure. The method also includes forming a first mask layer covering a sidewall of the second composite structure and a surface portion of the first composite structure and exposing at least another surface portion of the first composite structure. In addition, the method includes 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. Further, the method includes etching a top first layer of the first composite layers and a top first layer of the second composite layers.