We have fabricated GaAs metal–semiconductor field‐effect transistors (MESFET’s) and GaAs/AlGaAs modulation‐doped field‐effect transistors (MODFET’s) with gate lengths of 50 and 100 nm. A JEOL 5DIIU electron‐beam lithography system was used in the fabrication of these nanometer transistors. This system has demonstrated a 30‐nm overlay accuracy and liftoff metal lines as narrow as 25 nm. The electrical measurement results showed a room temperature extrinsic transconductance (gm) of 540 mS/mm for the 100‐nm MESFET’s and over 600 mS/mm for the 100‐nm MODFET’s. The MESFET also exhibited a small signal gain of 16 dB at 18 GHz at the low‐noise bias point which is the highest ever reported for a MESFET. A significant short channel effect, however, has also been observed in these very short gate transistors. In this paper, transistor fabrication will be discussed and electrical results will be presented.