High density (7-10 NW/μm) SiNW arrays of up to 16 nanowires vertically stacked with diameter widths below 20 nm have been successfully fabricated to create highly sensitive 3D FETs for biosensing applications. In order to take advantage of the increased sensing surface area that nanoscale 3D devices offer and improve the mechanical characteristics of the suspended sensing channels, fin-type structures (height/width ratio >1) are also being investigated. The vertical stacking allows higher utilization of the bulk Si. Higher output currents are expected as the number of conduction channels increases. 3D TCAD simulations have been done for up to three channels to investigate different device characteristics to achieve high sensitivities. Both NWs and Fins have been found to offer very high sensitivities through simulations especially for short (2 μm) channels, low channel doping concentrations (boron: 10 15 cm -3), and thin structures (width <30 nm) when applying an external sensing gate potential variation of ΔΨ = 90 mV. © 2012 Elsevier B.V. All rights reserved.