Bipolar transistor structure and radio frequency amplifier

A semiconductor device, comprising:

• an active region, wherein the active region comprises:
• a semiconductor layer, having a first surface, wherein the semiconductor layer comprises a collector layer, a base layer and an emitter layer sequentially stacked in that order;
• and the first surface is a surface of the emitter layer facing away from the base layer;
• an emitter mesa, disposed on the emitter layer;
• an emitter electrode, disposed on the emitter mesa;
• an interlayer dielectric layer, at least partially covering a top surface of the emitter electrode, and extends along a side surface of the emitter electrode to cover a part of the first surface exposed outside the emitter electrode;
• wherein the interlayer dielectric layer defines an opening;
• and
• a base electrode, connected to the base layer through the opening, and extending laterally to directly cover at least a part of an upper surface of the interlayer dielectric layer adjacent to the opening;
• and
• wherein in the semiconductor device, D1 is a spacing between the opening and the emitter mesa, D2 is a spacing between a part of the base electrode on the interlayer dielectric layer and the emitter mesa, and D2 is smaller than D1.