An impurity element imparting one conductivity type is included in a layer close to a gate insulating film of layers with high crystallinity, so that a channel formation region is formed not in a layer with low crystallinity which is formed at the beginning of film formation but in a layer with high...http://www.google.com/patents/US20090140256?utm_source=gb-gplus-sharePatent US20090140256 - THIN FILM TRANSISTOR AND SEMICONDUCTOR DEVICE
