Semiconductor integrated circuits (110) or assemblies are disposed at least partially in cavities between two interposers (120). Conductive vias (204M) pass through at least one of the interposers or at least through the interposer's substrate, and reach a semiconductor integrated circuit or an assembly. Other conductive vias (204M.1) pass at least partially through multiple interposers and are connected to conductive vias that reach, or are capacitively coupled to, a semiconductor IC or an assembly. Other features are also provided.