A semiconductor device includes first conductive lines and first and second insulation patterns on a substrate, first structures spaced apart from each other on the first conductive lines, a variable resistance pattern on the first structures, and a second electrode on the variable resistance pattern. The first conductive lines extend in a first direction. The first structures include a switching pattern and a first electrode sequentially stacked. The first insulation pattern fills a space between the first structures in a second direction and the first insulation pattern has a first top surface higher than a top surface of the first structures. The second insulation pattern fills a space between the first structures in the first direction, and the second insulation pattern has a second top surface higher than a top surface of the first structures. The variable resistance pattern fills an opening defined by the first and second insulation patterns.