A polycrystalline MgZnO/ZnO bi-layer was deposited by using a RF co-magnetron sputtering method and the MgZnO/ZnO bi-layer TFTs were fabricated on the thermally oxidized silicon substrate. The performances with varying the thickness of ZnO layer were investigated. In this result, the MgZnO/ZnO bi-layer TFTs which the content of Mg is about 2.5 at % have shown the enhancement characteristics of high mobility (6.77-7.56 cm(2) V-1 s(-1)) and low sub-threshold swing (0.57-0.69 V decade(-1)) compare of the ZnO single layer TFT (mu(FE) = 5.38 cm(2) V-1 s(-1); S.S. = 0.86 V decade(-1)). Moreover, in the results of the positive bias stress, the Delta V-on shift (4.8 V) of MgZnO/ZnO bi-layer is the 2 V lower than ZnO single layer TFT (Delta V-on = 6.1 V). It reveals that the stability of the MgZnO/ZnO bi-layer TFT enhanced compared to that of the ZnO single layer TFT. (C) 2015 Elsevier B.V. All rights reserved.