The present invention is an array substrate for use in a liquid crystal display device, which includes a gate electrode, a gate line and a gate pad on a substrate, wherein the gate electrode, the gate line and the gate pad have a double-layered structure consisting of a first metal layer and a first barrier metal layer in series from the substrate, and wherein the first metal is one of aluminum and aluminum alloy; a gate insulation layer on the substrate covering the gate electrode, gate line and gate pad; an active layer and an ohmic contact layer sequentially formed on the gate insulation layer and over the gate electrode; a data line on the gate insulation layer perpendicularly crossing the gate line, source and drain electrodes contacting the ohmic contact layer, and a data pad on the gate insulation layer, wherein the data line, the source and drain electrode and the data pad have a double-layered structure consisting of a second barrier metal layer and a second metal layer of copper; a passivation layer formed on the gate insulation layer to cover the data line, source and drain electrodes, and data pad, wherein the passivation layer has a drain contact hole exposing a portion of the drain electrode, a gate pad contact hole exposing a portion of the gate pad, and a data pad contact hole exposing a portion of the data pad; and a pixel electrode, a gate pad terminal and a data pad terminal on the passivation layer, all of which are formed of a transparent conductive material on the passivation layer.