An important prerequisite for the design of digital integrated circuits is the ability to control the threshold voltage of the individual transistors during manufacturing. To address the problem of controlling the threshold voltage of low-voltage organic transistors we have synthesized a fluoroalkylphosphonic acid that forms self-assembled monolayers on patterned, plasma-oxidized aluminum gate electrodes for use as high-capacitance, low-temperature gate dielectrics in p-channel and n-channel organic transistors. Compared with alkyl phosphonic acid-based monolayers, the strong electron-withdrawing character of the fluoroalkyl monolayers causes a change in the threshold voltage of the transistors by about 1 V, i.e. almost half of the supply voltage.