Provided are semiconductor devices and methods of fabricating the same. The device may include lower interconnection lines, upper interconnection lines crossing the lower interconnection lines, selection elements disposed at intersections, respectively, of the lower and upper interconnection lines, and memory elements interposed between the selection elements and the upper interconnection lines, respectively. Each of the selection elements may be realized using a semiconductor pattern having a first sidewall, in which a first lower width is smaller than a first upper width, and a second sidewall, in which a second lower width is greater than a second upper width, the first and second sidewalls crossing each other.