The aim of the present study is to determine the pre-irradiation threshold voltages of the RadFET dosimeters with gate oxide composed of high-k dielectrics and compare the results with the traditional sensors, the gate oxide of which is composed of SiO2. The effects of the p + regions with different concentration, depth and length on the electrical characteristic of the RadFETs were also investigated in the study. For these purposes, Al2O3, HfO2 high-k dielectrics and SiO2 with the thicknesses of 400 nm were used as the sensitive regions of the dosimeters. The sensors were designed in the Silvaco TCAD simulation program. While the lengths of the p + regions changed the Id-Vg characteristics of the RADFETs, the depths and concentrations until a certain value of these regions did not play an important role in electrical characteristic. The lowest threshold voltages obtained from the SiO2, Al2O3 and HfO2-RadFETs were found to be-5.22,-3.63, and-3.10 V, respectively. These results demonstrated that RadFETs with high-k dielectrics may be promising candidate for the new generated dosimeters in terms of broader measurable dose range providing their radiation tests.