A liquid crystal display device having a switching element in a pixel portion and a CMOS element in a driving portion includes: a substrate; a gate electrode on the substrate; a gate insulating layer on the gate electrode; a polycrystalline silicon layer on the gate insulating layer, the polycrystalline silicon layer having an active region in a central portion corresponding to the gate electrode and an ohmic contact region at side portions of the active region; an interlayer insulating layer having a set of contact holes for contacting the polycrystalline silicon layer at the side portions; and source and drain electrodes spaced apart from each other on the interlayer insulating layer, the source and drain electrodes contacting the polycrystalline silicon layer through the set of contact holes.