A poly-silicon (poly-Si) thin film transistor (TFT) having a back bias effect is provided in order to enhance characteristics of a leakage current, a sub-threshold slope, and an on-current. The poly-Si TFT includes a glass substrate, an island type buried electrode pad formed of an conductive material on one side of the glass substrate where the back bias voltage is applied, a buffer layer formed of an insulation material on the whole surface of the glass substrate, and a poly-Si TFT formed on the upper portion of the buffer layer. A method of fabricating the TFT is also provided.