A top-down nanofabrication approach involving molecular beam epitaxy and electron beam lithography was used to obtain silicon nanowire-based back gate field-effect transistors with Schottky contacts on silicon-on-insulator (SOI) wafers. The resulting device is applied in biomolecular detection based on the changes in the drain-source current (IDS). In this context, we have explained the physical mechanisms of charge carrier transport in the nanowire using energy band diagrams and numerical 2D simulations in TCAD. The results of the experiment and numerical modeling matched well and may be used to develop novel types of nanowire-based biosensors. Display omitted •A simple approach for fabrication of a silicon nanowire field-effect transistor for protein detection.•An evaluation of the biosensor performance with model molecules.•An explanation of electrical detection mechanism.•A demonstration of the energy bands shifting.•2D simulation considering the biosensor surface charge concentration.