In a method of fabricating a thin film transistor array substrate for a liquid crystal display, a gate line assembly is formed on a substrate with a chrome-based under-layer and an aluminum alloy-based over-layer while proceeding in the horizontal direction. The gate line assembly has gate lines, and gate electrodes, and gate pads. A gate insulating layer is deposited onto the insulating substrate such that the gate insulating layer covers the gate line assembly. A semiconductor layer and an ohmic contact layer are sequentially formed on the gate insulating layer. A data line assembly is formed on the ohmic contact layer with a chrome-based under-layer and an aluminum alloy-based over-layer. The data line assembly has data lines crossing over the gate lines, source electrodes, drain electrodes, and data pads. A protective layer is deposited onto the substrate, and patterned to thereby form contact holes exposing the drain electrodes, the gate pads, and the data pads. The sidewall of the under-layers for the gate line assembly and the data line assembly is exposed through the contact holes. An IZO-based layer is deposited onto the substrate, and patterned to thereby form pixel electrodes, subsidiary gate pads, and subsidiary data pads. The pixel electrodes are connected to the sidewall of the drain electrodes, and the subsidiary gate and data pads are connected to the sidewall of the gate and the data pads.