International audienceUltrathin bipolar + MOS (BiMOS) transistors were fabricated with 28-nm Ultra Thin Body and Buried oxide (UTBB) FD-SOI high-k metal gate technology for the first time. We evaluate the device behavior through dc/transmission line pulse measurements and 3-D TCAD simulations. The BiMOS demonstrates excellent MOS and hybrid behavior, with base as potential reference, exhibiting modulated apparent gain β A (~7 × 10 7 for the smallest base width) that can be controlled by the front and/or back gates. The mechanism of operation and further device optimizations are discussed. In addition, the device can work in four-gate FET mode with the two lateral junctions controlling the channel formation. For electrostatic discharge appli...