A lateral bipolar junction transistor is fabricated using a semiconductor-on-insulator substrate. The transistor includes a germanium gradient within a doped silicon base region, there being an increasing germanium content in the direction of the collector region of the transistor. The use of a substrate including parallel silicon fins to fabricate lateral bipolar junction transistors facilitates the inclusion of both CMOS FinFET devices and lateral bipolar junction transistors having graded silicon germanium base regions on the same chip.