A thin film transistor array panel is provided, which includes a plurality of gate lines, a plurality of common electrodes, a gate insulating layer covering the gate lines and the common electrodes, a plurality of semiconductor layers formed on the gate insulating layer, a plurality of data lines including a plurality of source electrodes and formed on the semiconductor layer, a plurality of drain electrodes formed on the semiconductor layer, and a plurality of pixel electrodes overlapping the common electrodes and connected to the drain electrodes. Because the common electrodes are made of ITON, IZON, or a-ITON, or a double layer of ITO/ITON, IZO/IZON, or a-a-ITO/a-ITON, when H2 or SiH4 are injected to form a silicon nitride (SiNX) layer on the common electrodes, the opaque metal Sn or Zn is not produced on the surfaces of the common electrode.