A thin-film transistor (100A, E, F, G, H, I; 200A, B; 300), comprising: a first gate electrode (121A, E, F, G, H, I; 221A, B; 321); a first gate insulating layer (163A, E, F, G, H, I; 263A, B; 363) disposed on the first gate electrode; a first oxide semiconductor layer (141A, E, F, G, H, I; 241A, B; 341) and a second oxide semiconductor layer (151A, E, F, G, H, I; 251A, B; 351) disposed on the first gate insulating layer; a first barrier layer (142A, E, F, G, H; 342) interposed between the first gate insulating layer and the first oxide semiconductor layer, wherein the first barrier layer (142A, E, F, G, H; 342) has a maximum valance band value (V max) lower than that of the first oxide semiconductor layer and the first gate insulating layer when the thin-film transistor is an N-type thin-film transistor, and wherein the first barrier layer (142A, E, F, G, H; 342) has a maximum conduction band value (C max) greater than that of the first oxide semiconductor layer and the first gate insulating layer when the thin-film transistor is a P-type thin-film transistor; an intermediate barrier layer (152A, E, F, G, H; 1421; 252A, B; 352) separating the first and second oxide semiconductor layers, wherein the intermediate barrier layer (152A, E, F, G, H, I; 252A, B; 352) has a lower maximum valance band value (V max) than a maximum valance band value (V max) of the first and second oxide semiconductor layers when the thin-film transistor is an N-type thin-film transistor, and the intermediate barrier layer (152A, E, F, G, H, I; 252A, B; 352) has a higher maximum conduction band value (C max) than the first and second oxide semiconductor layers when the thin-film transistor is a P-type thin-film transistor; a second gate insulating layer (161A, E, F, G, H, I; 261A, B; 361) disposed on the second oxide semiconductor layer; a second gate electrode (122A, E, F, G, H, I; 222A, B; 322) disposed on the second gate insulating layer, the second gate electrode electrically connected to the first gate electrode; a source electrode (131A, E, F, G, H, I; 231A, B; 331) electrically connected to the first and second oxide semiconductor layers; and a drain electrode (132A, E, F, G, H, I; 232A, B; 332) electrically connected to the first and second oxide semiconductor layers. a first gate electrode (121A, E, F, G, H, I; 221A, B; 321); a first gate insulating layer (163A, E, F, G, H, I; 263A, B; 363) disposed on the first gate electrode; a first oxide semiconductor layer (141A, E, F, G, H, I; 241A, B; 341) and a second oxide semiconductor layer (151A, E, F, G, H, I; 251A, B; 351) disposed on the first gate insulating layer; a first barrier layer (142A, E, F, G, H; 342) interposed between the first gate insulating layer and the first oxide semiconductor layer, wherein the first barrier layer (142A, E, F, G, H; 342) has a maximum valance band value (V max) lower than that of the first oxide semiconductor layer and the first gate insulating layer when the thin-film transistor is an N-type thin-film transistor, and wherein the first barrier layer (142A, E, F, G, H; 342) has a maximum conduction band value (C max) greater than that of the first oxide semiconductor layer and the first gate insulating layer when the thin-film transistor is a P-type thin-film transistor; an intermediate barrier layer (152A, E, F, G, H; 1421; 252A, B; 352) separating the first and second oxide semiconductor layers, wherein the intermediate barrier layer (152A, E, F, G, H, I; 252A, B; 352) has a lower maximum valance band value (V max) than a maximum valance band value (V max) of the first and second oxide semiconductor layers when the thin-film transistor is an N-type thin-film transistor, and the intermediate barrier layer (152A, E, F, G, H, I; 252A, B; 352) has a higher maximum conduction band value (C max) than the first and second oxide semiconductor layers when the thin-film transistor is a P-type thin-film transistor; a second gate insulating layer (161A, E, F, G, H, I; 261A, B; 361) disposed on the second oxide semiconductor layer; a second gate electrode (122A, E, F, G, H, I; 222A, B; 322) disposed on the second gate insulating layer, the second gate electrode electrically connected to the first gate electrode; a source electrode (131A, E, F, G, H, I; 231A, B; 331) electrically connected to the first and second oxide semiconductor layers; and a drain electrode (132A, E, F, G, H, I; 232A, B; 332) electrically connected to the first and second oxide semiconductor layers.