Abstract: The invention relates to a method of manufacturing a bipolar transistor on a semiconductor substrate (11) which is provided with a first, a second and a third layer (1,2,3) of a first, second and third semiconductor material respectively, all of a first conductivity type. A first portion of the second layer (2) is transformed into a buried isolation region (15) comprising a first electrically insulating material. A first semiconductor region (6) of the first conductivity type, comprising, for example, a collector region, is formed from a second portion of the second layer (2) adjoining the buried isolation region (15) and a portion of the first layer (1) adjoining the second portion of the second layer (2). Then a base region (7) is formed on the buried isolation region (15) and on the first semiconductor region (6) by transforming the third layer (3) into a second conductivity type, which is opposite to the first conductivity type.