The invention relates to a bipolar transistor structure which includes a layer of semiconductor material having a single crystal raised base, a single crystal or polycrystalline emitter and adjacent polycrystalline regions which provide an electrical connection to the emitter. The invention also relates to the method of fabricating such a structure and includes the step of depositing a conformal layer of semiconductor material of one conductivity type over a region of opposite conductivity and over insulation such that single crystal and polycrystalline regions form over single crystal material and insulation, respectively. In a subsequent step, a layer of opposite conductivity type semiconductor material is deposited on the first layer forming single crystal or polycrystalline material over single crystal and polycrystalline material over polycrystalline. Then, in a final step, the structure is subjected to an out-diffusion step which simultaneously forms a single crystal emitter region of opposite conductivity type, a p-n junction in the one conductivity type single crystal region and regions of opposite conductivity type which act as an interconnection to the emitter region.