A method for fabricating a three-dimensional semiconductor memory device including three-dimensionally arranged transistors includes forming a thin film structure comprising a plurality of thin films on a semiconductor substrate, patterning the thin film structure such that a penetration region is formed to expose the semiconductor substrate, forming a polycrystalline semiconductor layer to cover the resultant structure where the penetration region is formed, patterning the semiconductor layer to locally form a semiconductor pattern within the penetration region, and performing a post-treatment process to treat the semiconductor layer or the semiconductor pattern with a post-treatment material containing hydrogen or deuterium.