A thin film transistor substrate includes a substrate, a data line disposed on the substrate and which extends substantially in a predetermined direction, a light blocking layer disposed on the substrate and including a metal oxide including zinc manganese oxide, zinc cadmium oxide, zinc phosphorus oxide or zinc tin oxide, a gate electrode disposed on the light blocking layer, a signal electrode including a source electrode and a drain electrode spaced apart from the source electrode, where the source electrode is connected to the data line, and a semiconductor pattern disposed between the source electrode and the drain electrode.