We propose new poly-Si TFT's with selectively doped region in the center of channel in order to reduce large leakage current. In proposed TFT's, the selectively doped region redistributes total induced electric field in the channel. For VGS<0, VDS> 0 in the n-channel proposed TFT's, most of the high electric field applies in the depletion regions which exist the drain/undoped region and undoped region/selectively doped region which faces to the source. Comparing with conventional TFT's, the electric field induced near the drain junction reduces to about 1/2, therefore, electron-hole pairs generated in drain junction are considerably reduced. Furthermore, the ON-current of proposed TFT's is the same or slightly lower than that of conventional ones. Consequently, the experimental data show the considerable improvement of the ON/OFF current ratio.