A memory device includes a variable resistance layer and a selection device layer electrically connected to the variable resistance layer. The memory device further included a chalcogenide switching material that reduces leakage current and has, for example, a composition according to chemical formula 1 below, [GeXSiY(AsaTe1-a)Z](1-U)[N]U  (1) (where 0.05≤X≤0.1, 0.15≤Y≤0.25, 0.7≤Z≤0.8, X+Y+Z=1, 0.45≤a≤0.6, and 0.08≤U≤0.2).