Lateral bipolar transistor

1. A lateral bipolar transistor formed over a substrate of an SOI structure having a silicon layer provided over an embedded insulating film layer, comprising:

emitter diffusion regions formed in the substrate;

a base drawing diffusion region formed at a position away from each of the emitter diffusion regions;

isolation insulating films that reach the embedded insulating film layer and are formed between the emitter diffusion regions and the base drawing diffusion region;

a base diffusion region including, on both sides of the isolation insulating films, two end areas respectively brought into contact with the side faces of the isolation insulating films while ensuring electrical connections to the base drawing diffusion region, and central areas formed integrally with the two end areas so as to cover the peripheries of the emitter diffusion regions; and

a collector diffusion region at least formed around the central areas of the base diffusion region.

2. The lateral bipolar transistor according to claim 1 , wherein the emitter diffusion regions and the isolation insulting films are respectively provided on both sides of the base drawing diffusion region,

wherein the base diffusion region is formed in a ring form so as to surround the peripheries of the base drawing diffusion region, the two isolation insulating films disposed on both sides of the base drawing diffusion region and the two emitter diffusion regions disposed outside the isolation insulating films, and

wherein the collector diffusion region is formed in ring form so as to cover the periphery of the base diffusion region.

3. The lateral bipolar transistor according to claim 2 , further including a base wiring provided with respect to the base drawing diffusion region;

an emitter wiring provided in common with all of the emitter diffusion regions; and

a collector wiring provided with respect to the collector diffusion region.

4. The lateral bipolar transistor according to claim 1 , wherein the central areas of the base diffusion regions respectively have three sides connected to one another so as to surround the emitter diffusion regions, and

wherein connecting portions of the three sides are respectively brought into corner-cut shapes.

5. The lateral bipolar transistor according to claim 1 , wherein each of the base diffusion regions is prepared in the form of a first conduction type,

wherein a MOS transistor which includes a gate insulating film and a gate conductive layer prepared in the form of a second conduction type different from the first conduction type and is constructed so as to form a channel of the second conduction type, is formed over the substrate, and

wherein the lateral bipolar transistor further includes an insulating film which covers the surfaces of the base diffusion regions, and conductive layers formed over the insulating film in a state in which the characteristic of the second conduction type is suppressed as compared with the gate conductive layer.

6. The lateral bipolar transistor according to claim 5 , wherein the gate conductive layers over the base diffusion regions are intrinsic from the viewpoint of a conduction type.

7. The lateral bipolar transistor according to claim 5 , wherein the conductive layers over the base diffusion regions are prepared in the first conduction type the same as the base diffusion regions.