Double-heterojunction bipolar transistor and preparation method thereof

The invention provides a double-heterojunction bipolar transistor and a preparation method thereof. The method comprises the following steps: manufacturing an emitter region electrode on a wafer to be prepared, and performing wet etching on an emitter region in the wafer based on the emitter region electrode so as to expose a first boundary layer between the emitter region and a base region in the wafer; manufacturing a base region electrode on the upper surface of the first boundary layer, and performing wet etching on the first boundary layer and the base region in sequence based on the base region electrode so as to expose the second boundary layer between the base region and the collector region in the wafer; manufacturing a collector region electrode on the upper surface of the second boundary layer, and performing wet etching on the second boundary layer and the collector region in sequence based on the collector region electrode so as to expose the third boundary layer between the collector region and