Patent ID: 8450799

Claim:
A field effect transistor formed on an insulating substrate, comprising: an insulating substrate; a semiconductor thin film formed on the insulating substrate; a gate insulating film provided on the semiconductor thin film; a first gate electrode having a length and a width and being formed on the gate insulating film; a first region and a second region having a first conductivity type and being formed on or in the surface of the semiconductor thin film on opposite sides of the first gate electrode in the length direction thereof; a third region having a second conductivity type opposite the first conductivity type and being arranged side by side with the second region in the width direction of the first gate electrode; the third region and the second region being in contact with each other and making a low resistance junction, and the third region and the second region not being connected together via metal wiring and contact holes; a second gate electrode having a length and a width and being formed on the gate insulating film along the second and third regions; and a fourth region having the first conductivity type and being formed on or in the surface of the semiconductor thin film and on an opposite side of the second region with respect to the second gate electrode in a length direction thereof, one of the first and the fourth regions being used as an output region without any fixed bias potential to the third region according to a bi-directional circuit operation of the field effect transistor.