Bipolar transistor structure with base protruding from emitter/collector and methods to form same

A bipolar transistor structure comprising:

• a first emitter/collector (E/C) material above an insulator, the first E/C material having a first sidewall over the insulator and a second sidewall opposite the first sidewall and over the insulator;
• a first base above the insulator adjacent the first sidewall of the first E/C material;
• a second base above the insulator adjacent the second sidewall of the first E/C material;
• a second E/C material above the insulator and adjacent the first base, wherein a width of the first base between the first E/C material and the second E/C material is less than a width of the first E/C material, wherein the first base protrudes horizontally outward from an end of the first E/C material and an end of the second E/C material;
• a third E/C material above the insulator and adjacent the second base, wherein a width of the second base between the first E/C material and the third E/C material is less than a width of the first E/C material, and the second base protrudes horizontally outward from an end of the first E/C material and an end of the third E/C material;
• and
• a semiconductor-on-insulator (SOI) layer between each the first E/C material, the second E/C material, and third E/C material and the insulator.

A method of forming a bipolar transistor structure, the method comprising:

• forming a first emitter/collector (E/C) material above an insulator, the first E/C material having a first sidewall and a second sidewall over the insulator;
• forming a first base above the insulator adjacent the first sidewall of the first E/C material;
• forming a second base above the insulator adjacent the second sidewall of the first E/C material;
• and
• forming a second E/C material above the insulator and adjacent the first base, wherein a width of the first base between the first E/C material and the second E/C material is less than a width of the first E/C material, and the first base protrudes horizontally outward from an end of the first E/C material and an end of the second E/C material,
• wherein a semiconductor layer is between the first E/C material and the insulator and between the second E/C material and the insulator.