Method of manufacturing a semiconductor device, in which on a region of silicon oxide (5) situated next to a region of monocrystalline silicon (4) at the surface (3) of a semiconductor body (1), a non-monocrystalline auxiliary layer (8) is formed. The auxiliary layer is formed in two steps. In the first step, the silicon body is heated in an atmosphere comprising a gaseous arsenic compound; in the second step it is heated in an atmosphere comprising a gaseous silicon compound instead of said arsenic compound. Thus, the regions of silicon oxide are provided with an amorphous or polycrystalline silicon seed layer in a self-aligned manner.