This paper provides an analytical subthreshold model for trigate MOSFETs with thin buried oxide (BOX) for multithreshold (multi-Vth}) applications. This model shows a fairly good scalability in substrate bias and BOX thickness, which is crucial to the prediction of multi-Vth modulation through BOX. In addition, we demonstrate the application of our model in multi-Vth} device design for trigate GeOI p-MOSFETs with the body-effect coefficient (γ) over a wide range of design space efficiently examined. We have shown an enhanced multi-Vthmodulation behavior in trigate GeOI p-MOSFETs. Our study indicates that, for a given subthreshold swing and γ , the GeOI trigate p-MOSFET can possess a higher fin aspect ratio than the SOI counterpart.