In this letter, 5 nm-thick HZO ultra-thin ferroelectric capacitors with excellent remanent polarization (Pr) and reliability are presented. The TiN/HZO/TiN metal-ferroelectric-metal (MFM) capacitor stack was deposited consecutively in the same atomic layer deposition (ALD) system without breaking the vacuum (i.e. “in-situ” like) to improve the interface quality between TiN electrodes and HZO ferroelectric layer. The samples show high Pr of 20.5 μC/cm2 (i.e. 2Pr = 41 μC/cm2) under driving voltage of 3 V with low coercive voltage of approximately 0.6 V. The robustness of the MFM capacitor was presented by the outstanding endurance characteristics for keeping 2Pr value higher than 20 μC/cm2 after 1010 cycles at a high electric field of 5 MV/cm without breakdown, though the Pr values gradually degrade with cycles at low field (i.e. 2.4 MV/cm). The highly robust endurance characteristics of the 5nm-thick HZO MFM capacitor indicate the good interface quality achieved in this study.