A method of fabricating a thin-film transistor substrate including a thin-film semiconductor includes: forming a metal film mainly comprising Cu above a substrate; forming a source electrode and a drain electrode by processing the metal film in a predetermined shape; irradiating the source electrode and the drain electrode with nitrogen plasma; exposing surfaces of a top and an end portion of the source electrode and the drain electrode with silane (SiH4) gas; and forming an insulating layer comprising an oxide on the source electrode and the drain electrode.