Previous conflicting reports concerning fully depleted SOI device hot electron reliability may result from overestimation of channel electric field (Em). Experimental results using SOI MOSFET's with body contacts indicate that Emis just a weak function of thin-film SOI thickness (Tsi) and that Emcan be significantly lower than in a bulk device. with drain junction depth (X j) comparable to SOI's Tsi. The theoretical correlation between SOI MOSFET's gate current and substrate current are experimentally confirmed. This provides a means (IG) of studying Emin SOI device without body contacts. Thin-film SOI MOSFET's have better prospects for meeting breakdown voltage and hot-electron reliability requirements than previously thought.