SEMICONDUCTOR DEVICES

A semiconductor device includes a substrate including a first cell region, a second cell region adjacent to the first cell region in a first direction, and a comparison region adjacent the first and second cell regions in a second direction, a bit line in a first metal level on the substrate and extending in the first direction, and a first ground rail in a second metal level different from the first metal level. The first ground rail comprises a first sub-ground rail extending in the second direction on the first cell region, a second sub-ground rail extending in the second direction on the second cell region, a third sub-ground rail connecting the first sub-ground rail to the second sub-ground rail on the first and second cell regions, and a fourth sub-ground rail that branches off from the third sub-ground rail and extends in the second direction.