A protective layer having at least one hard-material layer is provided. The hard-material layer is formed from one or more of the following materials metal oxide, metal nitride, metal carbide, metal oxynitride, metal carbonitride, and metal oxycarbonitride. The hard-material layer has laterally closely cohesive, crystalline columns which grow perpendicular to the surface of the body. In some embodiments, the crystalline columns have a lateral dimension which is on average less than 1 .mu.m, preferably less than 200 nm, and which predominantly has crystal orientations which, in the case of columnar growth, have little tendency to widen out, the surface roughness of the hard-material layer having an R.sub.a value of less than 50 nm, preferably less than 20 nm.