A method of manufacturing a thin film transistor (“TFT”) substrate includes forming a first conductive pattern group including a gate electrode on a substrate, forming a gate insulating layer on the first conductive pattern group, forming a semiconductor layer and an ohmic contact layer on the gate insulating layer by patterning an amorphous silicon layer and an oxide semiconductor layer, forming a second conductive pattern group including a source electrode and a drain electrode on the ohmic contact layer by patterning a data metal layer, forming a protection layer including a contact hole on the second conductive pattern group, and forming a pixel electrode on the contact hole of the protection layer. The TFT substrate including the ohmic contact layer formed of an oxide semiconductor is further provided.