Aiming for improvement of the ZrO₂-based insulator properties as compared to the state-of-the-art ZrO₂/Al₂O₃/ZrO₂ stacks beyond 20 nm dynamic random access memory (DRAM) technology applications, ultra-thin (5 nm) ZrO₂/SrO/ZrO₂ stacks with TiN electrodes deposited by physical vapor deposition are addressed. By replacing the Al₂O₃ interlayer with SrO, the effective dielectric permittivity of the stack can be increased as indicated by electrical analysis. At the same time, no degradation of the insulating properties of the SrO-containing stacks and minor changes in the reliability, compared to an Al₂O₃ interlayer, are found. These results are indicating the possibility of further reducing the effective oxide thickness of the ZrO₂-based stacks to come close to 0.5 nm for future DRAM capacitors.