The transfer characteristics and low-frequency noise behavior of partially depleted silicon on insulator n-channel metal-oxide-semiconductor transistors after gamma-ray irradiation up to a total dose of 1M rad (Si) have been investigated in this paper. Due to the radiation-induced positive buried-oxide trapped charges and the interface traps, the back gate threshold voltage decreases from 44.72 to 12.88 V, and the electron field effect on mobility decreases from 473.7 to 419.8 cm(2)/V.s; while the sub-threshold swing increases from 2.47 to 3.93 V/dec. Based on the measurements of sub-threshold swing and the back gate threshold voltage, the variations of extracted radiation-induced buried oxide trapped charge and interface trap densities, are about 2.36 x 10(12) cm(-2) and 5.33 x 10(11) cm(-2) respectively. In addition, the normalized back gate flat-band voltage noise power spectral density is a sensitive function of radiation-induced buried oxide trapped charges and interface traps, which increases from 7 x 10(-10) V-2.Hz(-1) to 1.8 x 10(-9) V-2.Hz(-1). According to the carrier number fluctuation model, the extracted trap density near the interface between channel and buried oxide increases from 1.42 x 10(17) to 3.66 x 10(17) cm(-3).eV(-1). By considering the tunneling attenuation coefficient of the electron wave function and the tunneling depth of the electron in the buried oxide, the spatial distribution of trapped charges in the buried oxide before and after radiation are calculated and discussed.