A thin film transistor substrate, comprising: a first thin film transistor (T1) including a polycrystalline semiconductor layer (A1), a first gate electrode (Gl) on the polycrystalline semiconductor layer (A1), a first source electrode (S1) and a first drain electrode (D1); a first gate insulating layer (GI1) between the polycrystalline semiconductor layer (A1) and the first gate electrode (G1); a second thin film transistor (T2) including an oxide semiconductor layer (A2), a second gate electrode (G2) on the oxide semiconductor layer (A2), a second source electrode (S2) and a second drain electrode (D2); and an intermediate insulating layer (ILD) disposed on the first gate electrode (G1) and under the oxide semiconductor layer (A2), characterized in that the thin film transistor substrate further comprises: a second gate insulating layer (GI2) on the intermediate insulating layer (ILD) and under the first source electrode (S1), the first drain electrode (D1) and the second gate electrode (G2), wherein the second gate insulating layer (GI2) includes a first portion, a second portion, and a third portion physically separated from each other, wherein the first portion is disposed between the intermediate insulating layer (ILD) and the first source electrode (S1); wherein the second portion is disposed between the intermediate insulating layer (ILD) and the first drain electrode (D1); and wherein the third portion is disposed between the intermediate insulating layer (ILD) and the second gate electrode (G2). a first thin film transistor (T1) including a polycrystalline semiconductor layer (A1), a first gate electrode (Gl) on the polycrystalline semiconductor layer (A1), a first source electrode (S1) and a first drain electrode (D1); a first gate insulating layer (GI1) between the polycrystalline semiconductor layer (A1) and the first gate electrode (G1); a second thin film transistor (T2) including an oxide semiconductor layer (A2), a second gate electrode (G2) on the oxide semiconductor layer (A2), a second source electrode (S2) and a second drain electrode (D2); and an intermediate insulating layer (ILD) disposed on the first gate electrode (G1) and under the oxide semiconductor layer (A2), characterized in that the thin film transistor substrate further comprises: a second gate insulating layer (GI2) on the intermediate insulating layer (ILD) and under the first source electrode (S1), the first drain electrode (D1) and the second gate electrode (G2), wherein the second gate insulating layer (GI2) includes a first portion, a second portion, and a third portion physically separated from each other, wherein the first portion is disposed between the intermediate insulating layer (ILD) and the first source electrode (S1); wherein the second portion is disposed between the intermediate insulating layer (ILD) and the first drain electrode (D1); and wherein the third portion is disposed between the intermediate insulating layer (ILD) and the second gate electrode (G2). a second gate insulating layer (GI2) on the intermediate insulating layer (ILD) and under the first source electrode (S1), the first drain electrode (D1) and the second gate electrode (G2), wherein the second gate insulating layer (GI2) includes a first portion, a second portion, and a third portion physically separated from each other, wherein the first portion is disposed between the intermediate insulating layer (ILD) and the first source electrode (S1); wherein the second portion is disposed between the intermediate insulating layer (ILD) and the first drain electrode (D1); and wherein the third portion is disposed between the intermediate insulating layer (ILD) and the second gate electrode (G2). <EOS>