A semiconductor device includes a semiconductor substrate including a cell region and a core region adjacent to the cell region, active regions in the cell region and the core region, an interlayer insulating layer covering the active regions, upper cell contacts penetrating the interlayer insulating layer in the cell region, the upper cell contacts being adjacent to each other along a first direction and being electrically connected to the active regions, and core contacts penetrating the interlayer insulating layer in the active regions of the core region, the core contacts being adjacent to each other along the first direction and including upper connection core contacts electrically connected to the active regions, and dummy contacts adjacent to the upper connection core contacts, the dummy contacts being insulated from the active regions.