Abstract: A semiconductor device according to the invention comprises: a first semiconductor layer having a low impurity concentration formed on a semiconductor substrate; a second semiconductor layer of a first conductivity type formed on the first semiconductor layer and forming a heterojunction therewith; an emitter region and a collector region formed in the first and second semiconductor layers; and a semiconductor region of a second conductivity type formed in at least the second semiconductor layer between the emitter region and the collector region, wherein two-dimensional electron gas layers, induced in portions of the first semiconductor layer adjacent to the heterojunction and between the emitter region and the semiconductor region and between the collector region and the semiconductor region, are used as current paths, and a virtual base region is formed in the first semiconductor layer below the semiconductor region by majority carriers injected from the semiconductor region into the first semiconductor la

Abstract: An oscillator having a logic element that includes a charge-flow transistor and a load element, in combination, and that further includes a Schmitt trigger or the like connected to receive as input thereto an output from the logic element and to provide an output that is fed back as input to the logic element.