The present invention provides a method and a system based on a multi-gate field effect transistor for sensing molecules in a gas or liquid sample. The said FET transistor comprises dual gate lateral electrodes (and optionally a back gate electrode) located on the two sides of an active region, and a sensing surface on top of the said active region. Appling voltages to the lateral gate electrodes, creates a conductive channel in the active region, wherein the width and the lateral position of the said channel can be controlled. Enhanced sensing sensitivity is achieved by measuring the channels conductivity at a plurality of positions in the lateral direction. The use of an array of the said FTE for electronic nose is also disclosed.
