Experimental studies for two groups n-channel MOSFET are conducted. Each group, which have two devices from the same type, is exposed to dosages of gamma-ray ionizing radiation. The main objective of this study is to discuss the dynamic performance of these types under ionizing radiation for purpose of usage as a radiation dosimeter. Novelty of this study arisen from that the dynamic parameters such as threshold voltage, rise and fall times, different transconducatances and capacitances between device terminals are investigated. Because of gamma-ray irradiation, the surface and interface charges are arisen into MOSFET region. The threshold voltage is dependent on the MOSFET parameters, as it depends reversely on the oxide capacitance. From the obtained results, the channel width and length play an important role for determining all the dynamic parameters. One can notice that the majority of capacitances values are decreased. Consequently, the threshold voltage is decreased with the increase of radiation dose. From outcomes, the different transconductance values have different comportment according to the channel width and length into these adjacent regions. The devices under study are considered as a candidate to be a dosimeter for gamma-ray radiation.