High-quality silicon nanowire (NW) field-effect transistors (FETs) were designed and fabricated. Features of transport and modulation phenomena of the structures were studied using a number of techniques, including noise spectroscopy. Using the 1/f noise component level, the values of the volume trap densities in gate dielectric are estimated to be around 1 × 10 17 cm-3 eV-1. This result proves high quality of the investigated structures. Analysis of Lorentzian noise components of NW samples is used to characterize single trap and its parameters. A strong modulation of carrier concentration in the conducting channel under influence of even single carrier capture event has been revealed. Possibility of fine tuning of the transport properties of the sample with low-dose gamma irradiation has been shown. The gamma radiation treatment of the NW samples was applied as an effective technique to confirm the strong influence of trap charges on conductivity behavior in the channel of NW FETs. The results demonstrate that the modulation effects at the nanoscale enable effective changing of the channel conductivity by single capture events and thus are promising for future information technologies and ultra-sensitive single-molecular sensor applications.