Provided are a semiconductor device and a methods of forming and operating the semiconductor device. The semiconductor device may include active pillars extending from a semiconductor substrate and disposed two dimensionally disposed on the semiconductor substrate, upper interconnections connecting the active pillars along one direction, lower interconnections crossing the upper interconnections and disposed between the active pillars, word lines crossing the upper interconnections and disposed between the active pillars, and data storage patterns disposed between the word lines and the active pillars.