We propose a new quantum‐effect electronic device which consists of two one‐dimensional electron waveguides which, over a certain interaction length, come in close proximity to each other so that coherent quantum mechanical tunneling can take place between them. The degree of coupling between the two waveguides is controlled by modulating, through the field‐effect action of a gate, the height of the potential energy barrier which separates them. If an electron wave packet is injected into this device through one of the waveguides, then the probability density of the electron wave function will oscillate back and forth between the two waveguides as the packet advances. The gate voltage can be adjusted to achieve complete electron transfer at either of the two waveguides at the output of the device. The device, therefore, behaves as a current switch. In analogy with the optical dual‐channel directional coupler and the microwave dual‐guide multihole coupler, we call this device a quantum field‐effect directional coupler. First‐order calculations indicate that this device can be fabricated with state‐of‐the‐art nanolithography.