The development of a simple and reliable fabrication method for well-ordered semiconducting carbon nanotubes (CNTs) at room temperature is very important for future applications. We have succeeded in fabricating well-ordered CNT devices, which are linearly joined with two different diameter tubes and show a semiconducting characteristic at room temperature, by using well-ordered porous anodic alumina membranes and by annealing at a high temperature. The band gap was about 0.3 V and could be altered by changing the diameter ratio of the two tubes. These well-ordered semiconducting CNT devices could be used in fabrication of nanoscale electronic devices like field-effect transistors. (C) 2005 Elsevier B.V. All rights reserved.