Summary
Provided are a semiconductor device and a method of fabricating the same. At least one mold structure defining at least one first opening is formed on a substrate, wherein the mold structure comprises first mold patterns and second mold patterns that are sequentially and alternatingly stacked. Thereafter, side surfaces of the first mold patterns are selectively etched to form undercut regions between the second mold patterns. Then, a semiconductor layer is formed to cover a surface of the mold structure where the undercut regions are formed, and gate patterns are formed, which fill respective undercut regions where the semiconductor layer is formed.