Operation of a novel three‐terminal resonant tunneling device which consists of an AlGaAs/GaAs modulation‐doped structure grown on top of an AlAs/GaAs double‐barrier resonant tunneling heterostructure has been demonstrated. In this device, the drain‐to‐source voltage is used to directly control the bias across a resonant tunneling structure, while the gate voltage controls the number of carriers available for the tunneling process by modulating the density of carriers in a two‐dimensional electron gas. Device operation is demonstrated at 80 K as well as room temperature with peak current densities of 420 A/cm2and peak‐to‐valley ratios as high as 5:1. Operation into the hundred gigahertz range is predicted for an optimized device structure.