We have investigated a photo-leakage-current generation mechanism and tried to reduce it. It has been found that the I_<photo> of an offset poly-Si TFT is mainly generated in an offset region. By optimizing an offset length (about 0.5 μm), we have realized an offset poly-Si TFT with a high mobility (165 cm^2N-s) and a low I_<photo>(2.4×10^-11A at 1.4×10^5 lx). In order to control the offset length, lateral-etching method for the fabrication of a self-allgned offset structure, which we proposed previously, is very useful.
