Abstract: For the simple production of a back surface field it is proposed that a boron-containing diffusion source layer (2) be applied to the rear (RS) of a silicon wafer (1) and boron be driven into the wafer to a depth of about 1 to 5 .mu.m at 900 to 1200.degree. C. This is done in an oxygen-containing atmosphere so that an oxide layer (4) is formed on open silicon surfaces, obviating the need to mask the regions not to be doped. After the removal of the oxide and source layer, phosphorus diffusion takes place and the back contact (3) is produced. It contains aluminum and, during the burn-in process, provides good ohmic contact.