Patent ID: 6876039

Claim:
A variable threshold voltage complementary MOSFET with an SOI structure comprising: an SOI substrate main body having a support substrate, an insulating layer disposed on the support substrate, and island-shaped first and second silicon layers separately formed on the insulating layer; a first MOSFET formed of a fully depleted SOI where a first channel part is formed in the first silicon layer; a second MOSFET formed of a partially depleted SOI where a second channel part is formed in the second silicon layer, the second MOSFET configured as a complementary MOSFET with the first MOSFET; and an adjusted bias electrode disposed on the support substrate for applying to the SOI substrate main body an adjusted bias voltage that adjusts threshold voltage of the complementary MOSFET, wherein the first MOSFET has a first source region and a first drain region formed in the first silicon layer that sandwich the first channel part, and a first gate electrode disposed on the first channel part with a first gate insulating film sandwiched therebetween, and the second MOSFET has a second source region and a second drain region in the second silicon layer that sandwich the second channel part, a second gate electrode formed on the second channel part with a second gate insulating film sandwiched therebetween, a neutral region in the second silicon layer where a depletion layer is not formed so that adjusting of the threshold voltage of the second MOSFET responsive to the adjusted bias voltage is suppressed, and a suppressed voltage electrode disposed so as to contact with the neutral region for applying suppressed voltage to the neutral region to suppress the threshold voltage.