Abstract: Using Technology Computer Aided Design (TCAD) simulation, the total ionizing dose(TID)effect of bulk fin field-effect transistor(FinFET) is investigated in detail. Based on well calibrated device model generated, it is shown that FinFETs with high channel stop doping concentration, large fin width and tapered fin cross-section shape exhibit great TID immunity. Further gamma radiation simulation illustrates the evolution of trapped holes in shallow trench isolation (STI) oxide. In addition, circuit level response of TID effect is analyzed using Sentaurus mixed-mode simulation method. It is demonstrated that the performance and stability suffer adverse degeneration during TID.