PURPOSE: To easily obtain fine offset length with high precision, in a thin film transistor of offset gate structure.

CONSTITUTION: An undercut part 3a is formed under a gate electrode forming part 4 which determines the length of a channel region 6 between a source/drain region 5. An overhang part 4a of the gate electrode forming part 4 which corresponds with the undercut part 3a is etched, and a gate electrode 7 narrower than the width of the channel region 6 is formed. The offset length of the channel region 6 part of the part protruding outside the gate electrode 7 coincides almost with the protruding width of an overhang part 4a of the gate electrode forming part 4 which corresponds to the undercut part 3a of a gate insulating layer 3. Hence a fine offset length can be easily formed in the self-alignment manner with high precision, by etching the overhang part 4a.