To generate a very uniform copper deposit in particular in blind micro vias (BMVs) and trenches, an aqueous, acid bath for the electrolytic deposition of copper is provided, said bath containing at least one copper ion source, at least one acid ion source, at least one brightener compound and at least one leveler compound, wherein at least one leveler compound is selected from the group comprising synthetically produced non-functionalized peptides and synthetically produced functionalized peptides and synthetically produced functionalized amino acids.