We report on electron transport measurements in a planar resonant tunneling field‐effect transistor (PRESTFET) on a modulation‐doped GaAs/AlGaAs heterostructure. The PRESTFET is created by defining two independently biased, 60‐nm‐long Schottky gates separated by 60 nm, on top of the AlGaAs layer, which presents a tunable double‐barrier potential modulation to the electrons traveling from source to drain. Current measurements 4.2 K, as a function of gate bias, with both gates connected, exhibit strong multiple negative transconductance swings at a fixed drain bias below 5 mV, providing evidence of resonant tunneling through quantized states between the two barriers. Fixing the bias on one of the gates and scanning the second, or fixing the bias on both and varying the light intensity of a light‐emitting diode confirms this observation. In addition, a structure in the output conductance as a function of drain voltage at a fixed gate bias is clearly observed.