We have used irradiation by fast heavy ions and subsequent etching to prepare cylindrical channels in polymer/metal/polymer stacks. These channels were subsequently filled with insulator and semiconductor material, and then provided with suitable metallic contacts, to obtain a vertical field-effect transistor device. Preparation and first electronic results on this new device are reported. Typically 107 to 108 transistors per cm2 with a diameter of ∼100 nm can be obtained in this technique. The fabrication does not require lithography on the scale of a single transistor, and is suitable for large-area applications. The embedding in a soft polymer matrix results in a robust arrangement, whose electronic characteristics are largely insensitive to mechanical stress. At the present stage of development the smallest dimension of a single transistor grown by this technique is ∼50 nm. Further reduction of the device dimensions appears possible and, with it, observation of single electron effects in these devices.