We have investigated the low-frequency noise behavior of silicon nanowire metal-oxide-semiconductor field-effect transistors (NWFETs) by comparison with that of a planar FET. We have found that the NWFET exhibits lower noise intensity than the planar FET. By analyzing the factors influential to noise intensity, one of the most possible origins of this advantage of the NWFET results from the electron distribution in the channel in NWFET. Owing to quantum confinement, the position of charge-centroids in the channel of NWFET is located further from the interface, resulting in the lower trapping probability between the electrons and oxide traps. These results clearly demonstrate the advantage of three-dimensional structures in static and noise properties.