High frequency heterojunction bipolar transistor devices

A method for fabricating a lateral heterojunction bipolar transistor device, the method comprising:

• forming a buried oxide (BOX) layer over a substrate;
• forming a silicon-on-insulator (SOI) layer on the BOX layer;
• forming an oxide layer over some portion of the SOI layer;
• forming at least one gate over some other portion of the SOI layer;
• removing a first portion of the oxide layer and a first portion of the SOI layer to form a first opening;
• removing a second portion of the SOI layer from underneath the at least one gate to form a second opening between the at least one gate and the BOX layer;
• forming either an inverted T-shaped or an L-shaped emitter in the first opening;
• laterally forming a base in the second opening;
• forming a collector adjacent the base, wherein the collector and base are formed from different semiconductor materials having different bandgaps to form a heterojunction;
• removing a second portion of the oxide layer to form a collector contact hole;
• and
• forming 1) a collector contact in the collector contact hole, 2) a self-aligned base contact, and 2) an emitter contact, wherein the base contact is not dependent on photolithography alignment tolerances.

A lateral heterojunction bipolar transistor device comprising:

• a buried oxide (BOX) layer formed over a substrate;
• a silicon-on-insulator (SOI) layer formed on the BOX layer;
• an oxide layer formed over the SOI layer;
• a base formed on the BOX layer in a first region;
• a base contact formed in a cavity defined by a nitride spacer and an oxide inside spacer formed over the SOI layer and wherein the base contact is coupled to the base, wherein the base contact is aligned by the relative positions of the nitride spacer and the oxide inside spacer, wherein the base includes a semiconductor material with a bandgap less than silicon;
• and
• an inverted T-shaped or an L-shaped emitter formed on the BOX layer in a second region;
• and
• a collector formed on the BOX layer adjacent the base, wherein the collector and base are formed from different semiconductor materials having different bandgaps to form a heterojunction.