In this paper, the effects of total ionizing dose (TID) radiation on back-gate direct-current current-voltage (DCIV) curves in silicon on insulator (SOI) Metal-Oxide-Semiconductor Field-Effect Transistors (NMOSFETs) with different manufacture process are investigated. The magnitude of DCIV peak current increased with radiation dose increasing because of the elevated interface trap density. The shift of DCIV peak along with radiation dose resulted from the oxide trapped charge. It is concluded that DCIV curves of devices with different manufacture process change differently with TID radiation dose. DCIV curves of the PX devices with high-voltage P-well (PX) process showed larger shift to left with radiation dose compared with that of the PV devices with low-voltage P-well (PV) process. It is also observed that the DCIV peak current increased more slowly with radiation dose in the devices with high-voltage well (PX) process than that of low-voltage P-well (PV) process. It is illustrated that the high P-type impurity concentration near back interface makes it more difficult to break up silicon hydrogen bonds, which gives the PX devices superiority in resisting the build-up of interface traps. This study results indicated that increasing doping concentration of body region near the back-gate interface might be an alternative radiation hardening technique of SOI MOSFET devices to avoid the parasitic back transistors’ leakage.