Total ionizing dose induced single transistor latchup effects for 130 nm partially depleted silicon-on-insulator (PDSOI) NMOSFETs with the bodies floating were studied in this work.The latchup phenomenon strongly correlates with the bias configuration during irradiation.It is found that the high body doping concentration can make the devices less sensitive to the single transistor latchup effect,and the onset drain voltage at which latchup occurs can degrade as the total dose level rises.The mechanism of band-to-band tunneling (BBT) has been discussed.Two-dimensional simulations were conducted to evaluate the BBT effect.It is demonstrated that BBT combined with the positive trapped charge in the buried oxide (BOX) contributes a lot to the latchup effect.