We have studied dosimetric characteristics, linearity and performance of MOS structures as radiation sensors. This was performed by analyzing the correlation between irradiation dose and the shift in flat band voltage of MOS capacitors which were tested against gamma and beta radiations. Devices have been studied after repeated cycles of irradiation and annealing treatment under hydrogen and nitrogen ambient. Each cycle consists of gamma irradiation with 60 Gray-dose and an anneal at 200 degrees C for 30 min. Results obtained by high frequency C-V methods show that irradiation-annealing cycle correlates with the recovery of the measured signal. The charging-discharging mechanism during the cyclic treatment is discussed. The variation of the interface state density during the irradiation-annealing cycle was studied with a model based on conductance-voltage measurements. (c) 2007 Elsevier B.V. All rights reserved.