A thin film transistor substrate is disclosed, which comprises: a substrate; and plural thin film transistor units disposed on the substrate and respectively comprising: an active layer disposed on the substrate and made of polysilicon; an insulating layer disposed on the active layer; and a source electrode and a drain electrode disposed on the insulating layer, wherein the insulating layer comprises a first region corresponding to the active layer and a second region corresponding to a region outside the active layer, and a roughness of the first region is larger than that of the second region.