A field effect transistor comprising a semiconductor substrate comprising an electrically conducting channel layer therein; a plurality of source and drain fingers on a first face of the substrate, each finger separated from the adjacent finger by a gate channel; the gate channels comprising at least one active gate channel defined by a source finger and a drain finger arranged on the first face such that current is free to flow between them via the electrically conducting channel layer, and, a plurality of inactive gate channels, each inactive gate channel being defined by either two fingers of the same type or a source finger and a drain finger, the source finger and drain finger being arranged on the first face such that current is not free to flow between them via the electrically conducting channel layer; the gate channels being arranged such that each active gate channel has a gate channel on each side; each active gate channel comprising a gate therein for controlling current flow in the electrically conducting channel layer.