A semiconductor device includes a substrate; an active region extending on the substrate in a first direction; a protective layer on a lower surface of the substrate; an etch stop layer on a lower surface of the protective layer; a device isolation layer defining the active region; a gate structure on the active region and extending in a second direction, intersecting the first direction; a source/drain region on the active region on both lateral sides of the gate structure; a contact structure connected to the source/drain region; and a power transmission structure electrically connected to the contact structure.