A description is given of a method for producing isolation trenches (32, 34) with different sidewall dopings on a silicon-based substrate wafer for use in the trench-isolated smart power technology. In this case, a first trench (32) having a first width and a second trench (34) having a second width which is greater than the first width are formed using a hard mask (30). The sidewalls of the first and second trenches are doped in accordance with a first doping type in order to produce sidewalls having a first doping. A material layer (50, 51, 60, 61) is deposited with a thickness determined so as to fill the first trench (32) completely up to and beyond the hard mask and to maintain the gap (34a) in the second trench (34). By means of isotropic etching the material layer is removed from the second trench, but residual material of the material layer is maintained in the first trench. A further doping of sidewalls of the first trench or of the second trench in the presence of the residual material is then performed.