A method of fabricating a semiconductor device includes forming an interlayer insulating structure on a substrate, forming a contact hole that penetrates the interlayer insulating structure to expose the substrate, forming an amorphous silicon layer including a first portion and a second portion, the first portion covering a top surface of the substrate exposed by the contact hole, the second portion covering a sidewall of the contact hole, providing hydrogen atoms into the amorphous silicon layer, and crystallizing the first portion using the substrate as a seed.