Disclosed is an array substrate of an LCD, and a method for fabricating it, which simplifies the fabrication process, thereby reducing fabrication costs. The process is simplified because the array substrate does not have a passivation film. The thin film transistors on the array substrate each have an active layer that is protected from contamination by forming a channel insulation layer on the active layer through a dry-etching process. Further, the gate line, gate pad, and gate electrode may have a two-layer structure having a low-resistance metal layer and a barrier metal layer, or a three-layer structure having a low-resistance metal layer and two barrier metal layers.