A liquid crystal display (LCD) device capable of perventing impurities from permeating into a channel area of a switching element, the LCD device including: a gate electrode above a substrate; a semiconductor layer which overlaps the gate electrode; a drain electrode and a source electrode which overlap the semiconductor layer; an ohmic contact layer between the semiconductor layer and the drain electrode and between the semiconductor layer and the source electrode; a pixel electrode which is connected to one of the drain electrode and the source electrode; and a gate insulating layer between the gate electrode and the semiconductor layer, the gate insulating layer comprising fluorine. A concentration of the fluorine is decreasing, as the fluorine of the gate insulating layer being more adjacent to the substrate.