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 electrode on a substrate, wherein all of the gate electrode, the gate line and the gate pad electrode have a first barrier metal layer, a first copper layer, and a first out-diffusion film that covers and surrounds the first copper layer. In the liquid crystal display device, the pixel electrode, gate pad terminal and data pad terminal are formed of a transparent conductive material on a passivation layer.