The hot carrier effect in quasi-silicon-on-insulator (SOI) and conventional SOI power metal-oxide-semiconductor field-effect transistors (MOSFETs) was compared on the basis of experimental results. Device degradation caused by the hot carrier effect in the quasi-SOI power MOSFETs proved to be smaller than in the conventional SOI power MOSFETs because the former can suppress the activation of parasitic bipolar transistors.