Embodiments of the present disclosure relate to a thin film transistor array substrate and display device in which a semiconductor layer has a heterogeneous conductorization structure including heterogeneous conductorization portions having different electrical conductivity, and the gate insulator layer is not etched enough to expose the semiconductor layer between the source electrode part and the gate electrode part and between the drain electrode part and the gate electrode part, so that the possibility of damage to the semiconductor layer can be eliminated or reduced.