This paper describes a field effect transistor (FET) based sugar molecule sensor, using a totally synthetic and chemically stable sugar-detecting moiety phenylboronic acid (PBA). PBA was introduced to the FET sensing surfaces in two different ways. One is in the form of a thin copolymer gel layer directly attached to the FET gate insulator, the other method utilizes self-assembled monolayer (SAM) formed on an extended Au gate surface, a functional group of which was reacted with PBA. Reversible and prompt changes in the FET's electric characteristics were demonstrated in response to the change in glucose and sialic acid (Neu5Ac) concentrations depending on the pH of the milieu. The developed FET detection scheme could be extended to the construction of stable, readily miniaturizable, and label-free carbohydrate molecule sensing systems due to the ability of PBA moieties to interact with these molecules. (C) 2009 Elsevier B.V. All rights reserved.