Figure 1. A nanometer-scale field-effect-transistor is created by depositing a thin layer of semiconductor material on the tip of spear-shaped dual carbon nanoelectrodes fabricated by pyrolytic decomposition of butane inside Θ-nanopipettes. The two individually addressable electrodes serve as drain and source. Immobilising suitable recognition biomolecules on the semiconductor transistor channel yields selective FET biosensors.