Three-dimensional capacitive structures may be produced by forming a capacitive stack conformally over pores in a region of porous anodic oxide. The porous anodic oxide region is provided on a stack of electrically-conductive layers including an anodization-resistant layer and an interconnection layer. In the pores there is a position having restricted diameter quite close to the pore bottom. In a first percentage of the pores in the region of anodic oxide, a functional portion of the capacitive stack is formed so as to extend into the pores no further than the restricted-diameter position. Cracks that may be present in the anodization-resistant layer have reduced effect on the properties of the capacitive structure. Increased thickness of the anodization-resistant layer can be tolerated, enabling equivalent series resistance of the overall capacitive structure to be reduced.