Silicon-based semiconductor components - solar cells, protodectectors, LEDs - can be made with a porous layer on the adjacent substrate surface. Porous silicon can be produced by the electrochemical surface modification of flat silicon bodies. The physical properties of ultra-thin layers with nanoporous structures and their electrical or optical and opto-electric properties of high quality can be obtained. The production processes are compatible with preparation measures for other purposes. Such porous layers UPSL are ultra-thin - 20 to 100 or 150 nm - with pore diameters of up to 10 nm. Homogeneity is attained in both features. In addition, the type of conductivity and the doping concentration of the substrate material are independent. Said material may, for example, be pure Si, SiC or SiGe; it is single or polycrystalline and p conductive (solar cell, photodetector) or n conductive (LED). Layer thicknesses can be predetermined if a 0.1 to 0.7 molar aqueous electrolyte with a pH of 3.5 +/- 0.5 is used and the maximum anodisation current is kept between 0.3 and 2.1 mA/cm depending on its concentration. The treatment time can be adjusted via a reference value of flowed electric charge per unit area.