Increasing the alignment of thin films, which leads to anisotropy, is an attractive way to improve the performance of organic devices. A highly controllable and reproducible method to fabricate organic field effect transistors with large anisotropic ratios was proposed in this paper. The surface of the dielectric layer was etched to form patterns through conventional semiconductor processing. Transistors having current direction perpendicular to or parallel to the direction of the patterns were fabricated and characterized. The mobilities of these two kinds of transistors are 0.016 and 0.001 cm(2)/Vs respectively, which means the anisotropic ratio is 16. (C) 2007 Elsevier B.V. All rights reserved.