The performances of silicon junctionless nanowire transistors are evaluated in terms of short-channel effects, current drive, and gate capacitance. These devices are very easy to make, since there is no gradient of doping concentration in the nanowires. The physics of the device is explored and experimental results presented. Junction less devices are shown to have smaller short-channel effects than inversion-mode transistors with junctions. Comparison of carrier transport in the channel is made between junctionless nanowires and inversion-mode multigate field-effect transistors, and the benefits/drawbacks of bulk transport versus surface transport are addressed.