MBE regrowth on patternednp‐GaAs wafers has been used to fabricate GaAs/AlGaAs double barrier resonant tunnel diodes with a side‐gate in the plane of the quantum well. The physical diameters vary from 1 to 20 &mgr;m. For a nominally 1 &mgr;m diameter diode the peak current is reduced by more than 95% at a side‐gate voltage of −2 V at 1.5 K, which we estimate corresponds to an active tunnel region diameter of 75 nm ± 10 nm. At high gate biases additional structure appears in the conductance data. DifferentialI‐Vmeasurements show a linear dependence of the spacing of subsidiary peaks on gate bias indicating lateral quantum confinement. ©1996 American Institute of Physics.