In this paper, a novel structure named as quasidouble silicon-on-insulator metal-oxide-semiconductor transistor (SOI MOSFET) is proposed. Compared with the structure of normal SOI MOSFET, ultrathin oxide layers and p+ wells are added under the source and drain regions, which successfully isolate the source and drain from the buried oxide (BOX). The ultrathin oxide layers prevent the leakage current of the back gate and enhance its reliability. And the P+ wells acting as body ties suppress the floating body effect, but also decrease the resistance of the body contact. Transfer characteristic curve, output characteristic curve and the reliability of this structure are simulated by Sentaurus TCAD, and we compared the simulation results with that of the normal SOI MOSFET.