Enhanced dielectric constant and leakage suppression in symmetric ZrO2/Hf0.5Zr0.5O2/ZrO2 trilayers via mixed-phase engineering

HfO 2 -based dielectrics are promising for scaled capacitors, but increasing dielectric response often compromises leakage and reliability. Here, a single HZO film, an asymmetric ZrO 2 /HZO bilayer, and a symmetric ZrO 2 /HZO/ZrO 2 trilayer were compared while maintaining the same HZO thickness and, for S2 and S3, the same total ZrO 2 and high-k thicknesses. The symmetric trilayer exhibited an apparent large-signal zero-field dielectric constant of 42, approximately 3.5 times that of the single HZO film, with an M-shaped κ–E response and a transition field of ±0.9 MV/cm. Low-field minor P–E loops and zero-bias measurements at 100 kHz confirmed that S3 retained the largest sub-transition-field differential response, with an interfacial-layer-corrected effective permittivity of approximately 51 at 50 mV. GIXRD fitting showed progressive suppression of the monoclinic-related contribution from S1 to S3; sensitivity analyses preserved this trend despite model-dependent absolute values, while the overlapping o(111)/t(101) reflections could not be separated quantitatively. S3 also exhibited approximately two orders of magnitude lower leakage current and the longest Weibull characteristic lifetime. Thus, symmetric ZrO 2 redistribution provides a route toward high-response, low-leakage, and reliable ultrathin HZO capacitors.