PURPOSE: To provide a highly reliable SOI MOSFET which suppresses the influence of the thickness of a surface semiconductor layer on the electric properties while effectively reducing short channel effects, punch through, etc., and its manufacturing method. CONSTITUTION: In the SOI MOSFET which is composed of first conductivity channel regions P1-P3 made on the surface semiconductor layer arranged on an insulating substrate and depleted completely, a second conductivity source/ drain region 10 arranged across the channel regions, and a gate electrode 8 made through a gate insulating film 7 on the channel region, the channel region consists of the channel central regions P2 and the channel edge regions P1 and P3 which adjoin severally the source/drain regions 10 and where the concentration of impurities is set higher than that of the channel central region, and in the manufacturing method for the SOI MOSFET, both threshold voltages are set so that the change of the threshold voltage Vtho in the channel central region to the change of thickness of the surface semiconductor layer and the change of the threshold voltage Vthedge in the channel edge regions to the change of the thickness of the surface semiconductor layer may be a reverse code.
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