A top semiconductor layer is formed with two different thicknesses such that a step is formed underneath a body region of a semiconductor-on-insulator (SOI) field effect transistor at the interface between a top semiconductor layer and an underlying buried insulator layer. The interface and the accompanying interfacial defects in the body region provide recombination centers, which increase the recombination rate between the holes and electrons in the body region. Optionally, a spacer portion, comprising a material that functions as recombination centers, is formed on sidewalls of the step to provide an enhanced recombination rate between holes and electrons in the body region, which increases the bipolar breakdown voltage of a SOI field effect transistor.