A bipolar junction transistor relates to the technical field of a semiconductor power device. The transistor comprises an underlay, a collecting region, an emitting region, a base region, an emittingelectrode, a base electrode and a collecting electrode. The transistor is characterized in that a floating buried layer is arranged inside the base region; and the materials of the floating buried layer are different from that of the base region. The invention has the advantages of both good direct current characteristic and breakdown characteristic, namely both high current gain and higher breakdown voltage, and can be widely applied to the field of high-power converters (such as DC-DC converter and inverter).