Switching characteristics of an MNP three-layer structure (a Schottky-barrier transistor) have been investigated and a theory has been developed based on the concept of hole accumulation in the depletion layer of the Schottky-barrier and the subsequently induced tunnel-emission of electrons. The results of numerical calculations support the model and its high triggering sensitivity. Based on the theory, a new carrier-coupling device is proposed in which two or more MNP elements are linearly arrayed on a common substrate. By using MNP elements, many possible applications are anticipated which perform functions similar to plasma-coupled devices or charge-coupled devices.