The total dose radiation and annealing responses of the back transistor of Silicon-On-Insulator(SOI)pMOSFETs have been studied by comparing them with those of the back transistor of SOI n MOSFETs fabricated on the same wafer. The transistors were irradiated by60 Co γ-rays with various doses and the front transistors were biased in a Float-State and Off-State, respectively, during irradiation. The total dose radiation responses of the back transistors were characterized by their threshold voltage shifts. The results show that the total dose radiation response of the back transistor of SOI pMOSFETs, similar to that of SOI n MOSFETs, depends greatly on their bias conditions during irradiation. However, with the Float-State bias rather than the Off-State bias, the back transistors of SOI pMOSFETs reveal a much higher sensitivity to total dose radiation, which is contrary to the behavior of SOI n MOSFETs. In addition, it is also found that the total dose radiation effect of the back transistor of SOI pMOSFETs irradiated with Off-State bias, as well as that of the SOI n MOSFETs, increases as the channel length decreases. The annealing response of the back transistors after irradiation at room temperature without bias, as characterized by their threshold voltage shifts, indicates that there is a relatively complex annealing mechanism associated with channel length, type, and bias condition during irradiation. In particular, for all of the transistors irradiated with Off-State bias, their back transistors show an abnormal annealing effect during early annealing. All of these results have been discussed and analyzed in detail by the aid of simulation. The total dose radiation and annealing responses of the back transistor of Silicon-On-Insulator (SOI) pMOSFETs have been studied by comparing them with those of the back transistor of SOI n MOSFETs fabricated on the same wafer. -rays with various doses and the frontiers were biased in a Float-State and Off-State, respectively, during irradiation. The total dose radiation responses of the back transistors were characterized by their threshold voltage shifts. The results show that the total dose However, with the Float-State bias rather than the Off-State bias, the back transistors of SOI pMOSFETs reveal a much higher sensitivity to total dose radiation, which is contrary to the behavior of SOI n MOSFETs. In addition, it is also found that the total dose radiation effect of the back transi stor of SOI pMOSFETs irradiated with Off-State bias, as well as that of the SOI n MOSFETs, increases as the channel length decreases. The annealing response of the back transistors after irradiation at room temperature without bias, as characterized by their threshold voltage shifts , that that there is a relatively complex annealing mechanism associated with channel length, type, and bias condition during irradiation. All of these results have been discussed and analyzed in detail by the aid of simulation.