Methods of fabricating a semiconductor device are provided. The method includes alternately stacking first material layers and second material layers on a substrate to form a stacked structure, forming a through hole penetrating the stacked structure, forming a data storage layer on a sidewall of the through hole, forming a semiconductor pattern electrically connected to the substrate on an inner sidewall of the data storage layer, etching an upper portion of the data storage layer to form a first recessed region exposing an outer sidewall of the semiconductor pattern, and forming a first conductive layer in the first recessed region. Related devices are also disclosed.