A novel strategy to enhance the bias and illumination stress stability of oxide thin-film transistors (TFTs) is presented. The ultrathin positive charge barrier is employed to block the movement of photo-generated charges toward the interface between gate insulator and semiconductor under negative gate bias and illumination. This method can break through the limitation in stability enhancement caused by the inevitable oxygen vacancy and facilitates the fabrication of highly stable oxide TFTs at low process temperature. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3610476]