Abstract: A field effect transistor device comprising: a source electrode; a drain electrode; a semiconductive region comprising an organic semiconductor material and defining a channel of the device between the source electrode and the drain electrode; a first gate structure comprising a first gate electrode and a first dielectric region located between the first gate electrode and the semiconductive region; and a second gate structure comprising a second gate electrode and a second dielectric region located between the second gate electrode and the semiconductive region; whereby the conductance of the semiconductor region in the channel can be influenced by potentials applied separately or to both the first gate electrode and the second gate electrode.