A method of manufacturing an array substrate for a liquid crystal display device includes forming a gate electrode and a gate line on a substrate through a first mask process, forming a first insulating layer, an active layer, an ohmic contact layer, a buffer metallic layer, and a data line on the substrate including the gate electrode and the gate line through a second mask process, and forming a source electrode, a drain electrode, and a pixel electrode through a third mask process, the pixel electrode extending from the drain electrode, wherein the active layer is disposed over and within the gate electrode.