Transistors having bases with different shape top surfaces
AssigneeNational Semiconductor Corporation
InventorAli A. Iranmanesh
Life of this patent
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Abstract
A bipolar transistor is provided in which the emitters do not traverse the base but terminate inside the top surface of the base. Each emitter is L-shaped in some embodiments. The base top surface has a polygonal or circular outer boundary. The transistor has a long emitter perimeter available for base current flow and more than two emitter sides (e.g., five sides) available for base current flow. Further, the transistor has a large ratio of the emitter area to the base area. Consequently, the transistor has low noise, high gain, high frequency range, and a small size.
Claims6
A method for forming a transistor, said method comprising the steps of:
- forming a collector;
- forming a base overlying said collector, said base having a top surface;
- and
- forming a first emitter overlying said top surface of said base and comprising:
- a first portion which in plan view extends from a boundary of said top surface of said base inside said top surface;
- and
- a second portion which in plan view extends at an angle to said first portion.
A method for forming a transistor, said method comprising the steps of:
- forming a collector;
- forming a base overlying said collector, said base having a top surface having an outer boundary which in plan view is substantially a polygon having at least five sides;
- and
- forming an emitter overlying said top surface of said base so as to overlie a portion of said outer boundary of said top surface but not the entire outer boundary of said top surface.
A method for forming a transistor, said method comprising the steps of:
- forming a collector;
- forming a base overlying said collector, said base having a top surface having an outer boundary which in plan view is substantially circular;
- and
- forming an emitter overlying said top surface of said base so as to overlie a portion of said outer boundary of said top surface but not the entire outer boundary of said top surface.
Dependencies are inferred from the claim text.