An integrated circuit device includes a back side interconnection structure extending in a first horizontal direction. An active substrate includes a fin-type active area extending in the first horizontal direction on the back side interconnection structure. A metal silicide film is between the back side interconnection structure and the active substrate. A plurality of gate structures extends in a second horizontal direction perpendicular to the first horizontal direction on the active substrate. A first source/drain area and a second source/drain area are spaced apart from each other in the first horizontal direction with the plurality of gate structures therebetween on the active substrate. The first source/drain area directly contacts the active substrate. The second source/drain area is spaced apart from the active substrate and insulated from the active substrate.