Semiconductor devices include lower interconnections, upper interconnections crossing over the lower interconnections, selection components disposed at crossing points of the lower interconnections and the upper interconnections, respectively, and memory components disposed between the selection components and the upper interconnections. Each of the selection components may include a semiconductor pattern having a first sidewall and a second sidewall. The first sidewall of the semiconductor pattern may have a first upper width and a first lower width that is greater than the first upper width. The second sidewall of the semiconductor pattern may have a second upper width and a second lower width that is substantially equal to the second upper width.