A liquid crystal display device is disclosed, which comprises an upper substrate, a lower substrate, and a liquid crystal layer. The lower substrate has several pixel electrodes, metal lines, and switch elements thereon. Each switch element comprises a source electrode, a drain electrode, a gate electrode, and an opening between the source electrode and the drain electrode. A passivation layer covering the surface of the source electrode and the drain electrode forms two inclined planes separately on two sides. The two inclined planes face each other and are locating on a kink or step of the source electrode and drain electrode. The inclined planes also contact each other at the upper side of the opening. The inclinations of the inclined planes to the lower substrate are in a range from 5 to 50 degrees.