An array substrate for a display device includes an insulation substrate, a gate line formed on the insulation substrate, a data line crossing the gate line to define a pixel area, a thin film transistor including a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode, a passivation layer covering the gate line, the data line and the thin film transistor and including a drain contact hole to expose the drain electrode, and a pixel electrode formed on the pixel area and being connected to the drain contact hole through the drain contact hole. Each of the data line, the source electrode and the drain electrode includes a lower layer having copper and an upper layer covering upper and side surfaces of the lower layer, and the upper layer is thinner than the lower layer.