SEMICONDUCTOR DEVICE

A semiconductor device includes a substrate including active regions extending in a first direction; a device isolation layer surrounding the active regions on the substrate; gate structures intersecting the active regions and extending on the substrate in a second direction; source/drain regions on the active regions; contact plugs connected to the source/drain regions, respectively; a vertical buried structure penetrating through at least a portion of the device isolation layer, and in contact with the contact plugs; a vertical insulating layer covering at least a portion of side surfaces of the vertical buried structure; a horizontal buried structure below the vertical buried structure; a first conductive barrier covering at least a portion of an upper surface and side surfaces of the horizontal buried structure; and a metal-semiconductor compound pattern between the vertical buried structure and the first conductive barrier, wherein the vertical buried structure is between source/drain regions.