Cu(In,Ga)Se-2 (CIGS)-based thin-film solar modules are commonly deposited on float glass substrates at temperatures of approximately 550degreesC. For the preparation of flexible and monolithically integrated solar modules on metal foils. the substrates first have to be coated by an electrically insulating barrier. In this study. dielectric barrier layers of Al2O3 and SiOx were deposited on metal foils of Ti. Kovar(R) and ferritic Cr steel. The insulation properties were tested by sputtering small Mo contacts onto the barriers and measuring the resistance and breakdown voltages of the layers before and after CIGS deposition. Best insulating barriers could be achieved with 6-mum-thick combi layers of SiOx (plasma CVD)/SiOx (sol-gel) and SiOx (plasma CVD)/ Al2O3 (sputtered). These layers additionally act as diffusion barriers. Results of solar cell and module characterisation are presented to demonstrate the progress in barrier development.