<p>A method of fabricating a bipolar transistor in a first trench (11) is disclosed wherein only one photolithographic mask is applied which forms a first trench (11) and a second trench (12). A collector region (21) is formed self-aligned in the first trench (11) and the second trench (12). A base region (31) is formed self-aligned on a portion of the collector region (21), which is in the first trench (11). An emitter region (41) is formed self-aligned on a portion of the base region (31). A contact to the collector region (21) is formed in the second trench (12) and a contact to the base region (31) is formed in the first trench (11). The fabrication of the bipolar transistor may be integrated in a standard CMOS process.</p>
