Gate control characteristics of GaAs-based quantum wire transistors (QWRTrs) controlled by a nanometer-scale Schottky wrap gate (WPG) are investigated theoretically and experimentally. Gate bias dependence of the effective wire width of fabricated WPG QWRTrs determined theoretically as well as experimentally from Landau plots showed that the nanometer-scale WPG controls the potential very tightly near channel pinch-off and that the pinch-off threshold voltage is strongly dependent on the gate length, L-G, when L-G is shorter than 400 nm. The theory based on the three-dimensional (3D) potential simulation pointed out that Fermi level pinning on the semiconductor surface around the WPGs strongly affects the gate controllability in the nanometer-scale Schottky WPG structure. (C) 2002 Elsevier Science B.V. All rights reserved.