A liquid crystal display device includes a data line, a source electrode, a drain electrode, and a pixel electrode disposed on a lower substrate, an island-shaped semiconductor layer overlapping the source and drain electrodes, a gate insulating layer along an entire surface of the lower substrate including the semiconductor layer, a gate line and a gate electrode on the gate insulating layer, a passivation layer along an entire surface of the lower substrate including the gate line, an upper substrate facing the lower substrate, and a liquid crystal layer between the lower and upper substrates.