The invention provides a TFT electrode structure and its manufacturing method that can prevent metal diffusion occurring in the fabrication of a TFT, and thereby reduce the risk of contamination of the chemical vapor deposition process due to metallic ion diffusion. The transparent pixel electrode is formed after the gate electrode metal so that the pixel transparent electrode can be used as a barrier layer to prevent metal diffusion under high temperature from the gate electrode metal to adjacent insulating layers or the active layer. Further, the method used to form the transparent pixel electrode is a low-temperature physical vapor deposition process, which affected less by the processing environment, and the transparent pixel electrode is a conductive layer that is not affected by metal diffusion.