Provided are nanocrystal silicon layer structures formed using a plasma deposition technique, methods of forming the same, nonvolatile memory devices including the nanocrystal silicon layer structures, and methods of fabricating the nonvolatile memory devices. A method of forming a nanocrystal silicon layer structure includes forming a buffer layer on a substrate and forming a nanocrystal silicon layer on the buffer layer by a plasma deposition technique using silicon (Si)-containing gas and hydrogen (H2)-containing gas. In this method, the nanocrystal silicon layer can be directly deposited on a glass substrate using plasma vapor deposition without performing a post-processing process so that the fabrication of a nonvolatile memory device can be simplified, thereby reducing fabrication cost.