Bipolar transistor

1. A bipolar transistor, comprising a collector having a base layer provided thereon and a shallow trench isolation structure formed therein, and a base poly provided on the shallow trench isolation structure, wherein the shallow trench isolation structure defines a step such that a surface of the collector projects from the shallow trench isolation structure adjacent the collector.

2. The bipolar transistor according to claim 1 , wherein the base poly is a polysilicon layer.

3. The bipolar transistor according to claim 1 , wherein the base layer and the base poly are formed from SiGe.

4. The bipolar transistor according to claim 3 , wherein the base layer is formed from single crystal SiGe.

5. A method of manufacturing a bipolar transistor, the method comprising:

forming a shallow trench isolation structure in the collector;

etching the shallow trench isolation structure; and

growing an epitaxial layer over the collector that forms a base layer on a collector and a base poly layer on the etched shallow trench isolation structure,

wherein the step of etching comprises defining a step in the shallow trench isolation structure such that the collector projects from the shallow trench isolation structure adjacent the collector.

6. The method of claim 5 , wherein the step for growing the epitaxial layer grows a SiGe epitaxial layer such that the base layer comprises a single crystal SiGe layer and the base poly layer comprises polysilicon SiGe.

7. The method of claim 5 , further comprising the steps of:

forming a gate oxide layer over the collector;

forming a gate layer over the gate oxide, and

patterning and etching to remove the gate layer from over at least a portion of the collector, wherein said step of etching the shallow trench isolation comprises etching to remove the gate oxide layer from over the at least a portion of the collector to define said step in the shallow trench isolation structure.

8. A method of manufacturing a bipolar transistor, the method comprising:

forming a collector;

forming a shallow trench isolation structure in the collector;

etching the exposed portion of the shallow trench isolation structure to define a step in the shallow trench isolation structure such that a horizontal surface of the collector projects above the shallow trench isolation structure adjacent the collector; and

after etching the exposed portion of the shallow trench isolation structure, forming an epitaxial layer over the collector that forms a base layer on and in direct contact with the horizontal surface of the collector and a base poly layer on the etched portion of the shallow trench isolation structure.