Fabrication of flexible device structures and nanoscale size definition are presently among the most important and ambitious development goals in the IT field. We have recently prepared the vertical nanowire field effect transistor in the flexible polymer foils based on ion tracks. The high-energetic fast heavy ions were used to irradiate the 8μm PET foils and then the chemical etching method were employed to prepare cylindrical channels in these PET foils. These channels were subsequently filled with insulator material and semiconductor, 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 over 107 transistors per cm2 with the devices’ 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 and flexible applications.