Field plate in heterojunction bipolar transistor with improved break-down voltage

A method comprising:

• forming a substrate having a selectively implanted collector (SIC) and a collector separated by a shallow trench isolation (STI), a top portion of the STI is above the SIC and above the collector;
• forming a trench in the STI, the trench does not reach the SIC;
• forming a field plate in the trench;
• forming a base layer above the SIC and above the field plate, the base layer is directly on top of the SIC;
• forming a heterojunction bipolar transistor (HBT) structure above the SIC, the HBT includes an emitter, the emitter is directly on the base layer, and a portion of the field plate is below a bottom surface plane of the HBT structure;
• forming a fourth dielectric layer covering the HBT structure, the field plate and the collector;
• and
• forming an emitter contact, a field plate contact and a collector contact through the fourth dielectric layer, the emitter contact is in electrical connection with the emitter, the field plate contact is in electrical connection with the field plate, and the collector contact is in electrical connection with the collector.

A structure comprising:

• a substrate having a selectively implanted collector (SIC) and a collector separated by a shallow trench isolation (STI);
• a field plate in the STI, the field plate extends below a top surface of the SIC;
• a base layer directly on the SIC;
• a heterojunction bipolar transistor (HBT) structure above the SIC, the HBT includes an emitter, the emitter is directly on the base layer;
• a fourth dielectric layer covering the HBT structure, the field plate and the collector;
• and
• an emitter contact, a field plate contact and a collector contact extending through the fourth dielectric layer, the emitter contact is in electrical connection with the emitter, the field plate contact is in electrical connection with the field plate and the collector contact is in electrical connection with the collector.