THIN FILM TRANSISTOR, ITS MANUFACTURING METHOD, AND LIQUID CRYSTAL DISPLAY DEVICE USING IT

摘要

PROBLEM TO BE SOLVED: To provide a thin film transistor improved in performance and reliability by suppressing the OFF current (photoconductive current) when the channel region of the transistor is irradiated with light. SOLUTION: The thin film transistor has a polysilicon semiconductor layer on which a channel region and source and drain regions arranged on both sides of the channel region are formed. A depletion layer is formed between the channel region and drain region so that the width of the depletion layer may have a proportional relation with the photoconductive current which is generated when the channel region is irradiated with light. In order to suppress the photoconductive current to a prescribed allowable value or lower, the width of the depletion layer is adjusted to a value found based on the proportional relation or smaller.