A method for manufacturing a bipolar transistor, comprising the steps of: growing on the substrate a first semiconductor; depositing an encapsulation layer etchable with respect to the first semiconductor, forming a sacrificial block at the location of the base-emitter junction; exposing the first semiconductor around spacers formed around said block; forming a second semiconductor, then a third semiconductor etchable with respect to the second semiconductor layer, the encapsulation layer, and the spacers, the sum of the thicknesses of the second semiconductor and the sacrificial layer being substantially equal to the sum of the thicknesses of the encapsulation layer and of the sacrificial block; removing the block and the encapsulation layer; depositing a fourth semiconductor; removing the third semiconductor; and etching an insulating layer to maintain it on the emitter walls and between said emitter and the second semiconductor.