Heterojunction bipolar transistor using reverse emitter window

A method of manufacturing a heterojunction bipolar transistor comprising:

• providing a semiconductor substrate having a collector region;
• forming an intrinsic base region of a compound semiconductive material over the collector region;
• forming a reverse emitter window over the intrinsic base region;
• forming a first polysilicon layer over a portion of the intrinsic base region uncovered by the reverse emitter window;
• performing a chemical mechanical polish of the polysilicon layer to level the upper surface of the polysilicon layer with the upper surface of the reverse emitter window;
• recessing the polysilicon layer below the upper surface of the reverse emitter window to form an extrinsic base structure over the intrinsic base region uncovered by the reverse emitter window;
• growing a dielectric layer over the first polysilicon layer;
• processing the reverse emitter window to form an emitter window having a multi-layer reverse insulating spacer therein;
• forming a second polysilicon layer over the dielectric layer and into the emitter window;
• processing the second polysilicon layer to form an emitter structure;
• processing the first polysilicon layer to form an extrinsic base structure over a portion of the intrinsic base region beside and spaced from the emitter structure;
• forming an interlevel dielectric layer over the collector region, the extrinsic base structure, and the emitter structure;
• and
• forming connections through the interlayer dielectric layer to the collector region, the extrinsic base structure, and the emitter structure.