A vertical field effect transistor (VFET) including a first source/drain region, a channel structure upwardly protruding from the first source/drain region and configured to serve as a channel, the channel structure having a two-dimensional structure in a plan view, the channel structure having an opening at at least one side thereof, the channel structure including one or two first portions and one or more second portions, the one or two first portion extending in a first direction, and the one or more second portions connected to corresponding one or more of the one or more first portions and extending in a second direction, the second direction being different from the first direction, a gate structure horizontally surrounding the channel structure, and a second source/drain region upwardly on the channel structure may be provided.