The high quality SOI（silicon on insulator） materials were prepared with highly selective and self-stopping full isolation by porous oxidized silicon（FIPOS） technology. The PMOSFETs with different channel lengths were fabricated by the 2 μm CMOS process on the SOI wafers and their total dose 60Co γ- ray radiation characterietics were studied. The reaults show that the devices remain functional after 5kGy（Si） dose radiation

but the threshold voltage has a significant shift. The main factor causing this shift is the radiation- induced trapped- oxide charge in the gate oxide layer. The devices with different channel lengths have similar radiation characteristics. After room- temperature annealing for several hours

the threshold voltage has a little back- shift.