Field-Effect Transistors (FET) form an established technology for sensing applications. However, recent advancements and use of high-performance multi-gate MOSFETs (double-gate, FinFET, trigate, Gate-All-Around) in computing technology, instead of bulk MOSFETs, raise new opportunities and questions about the most suited device architectures for Sensing Integrated Circuits (SIC). In this work, we propose pH and ion sensors exploiting FinFETs fabricated on bulk silicon (Si) by a fully CMOS compatible approach, as an alternative to the widely investigated Silicon Nanowires (SiNW) on Silicon-On-Insulator (SOI) substrates. We also provide an analytical insight of the concept of sensitivity for the electronic integration of sensors. N-channel fully-depleted FinFETs with critical dimensions of the order of 20 nm and HfO2 as high-k gate insulator have been developed and characterized showing excellent electrical properties, subthreshold swing, SS ~ 70 mV/dec, and, on-to-off current ratio, Ion/Ioff ~ 106, at room temperature. The same FinFET architecture is validated as a highly sensitive, stable and reproducible pH sensor. An intrinsic sensitivity close to the Nernst limit, S = 57 mV/pH is achieved. The pH response in terms of output current reaches Sout = 60%. Long-term measurements have been performed over 4.5 days with a resulting drift in time δVth/δt = 0.10 mV/h. Finally, we show the capability to reproduce experimental data with an extended three-dimensional commercial Finite Element Analysis (FEA) simulator, in both dry and wet environments, which is useful for future advanced sensor design and optimization.