Abstract: The radiation response of 100 nm and 400 nmRADFETs was investigated at room temperature and elevated temperatures. A total radiation dose of 80 krad(Si) was reached with two different dose rates of 3 rad(Si)/s and 0.098 rad(Si)/s. The midgap technique was used to separate influence of the oxide trap charge and the interface trap charge. The microscopic mechanism of radiation response at elevated temperatures was analyzed. The annealing effect of the oxidetrap charge is the main reason for the nonlinear response. The changes of the oxidetrap charge with different oxide thicknesses have great difference, while the interfacetrap charge densities have little difference at elevated temperatures. The feasibility of using RADFETs at elevated temperatures was discussed, providing a reference for the application of RADFETs in elevated temperature environment.