A bottom-up approach starting with the development of new Hf precursors for plasma-enhanced atomic layer deposition (PEALD) processes for HfO₂ followed by in situ thin-film surface characterization of HfO₂ upon exposure to reactive gases via near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) is reported. The stability of thin films under simulated operational conditions is assessed, and the successful implementation of HfO₂ dielectric layers in metal-insulator-semiconductor (MIS) capacitors is demonstrated. Among the series of newly synthesized mono-guanidinato-tris-dialkyl-amido class of Hf precursors, one of them, namely, [Hf{²-(ⁱPrN)₂CNEtMe}(NEtMe)₃], was representatively utilized with oxygen plasma, resulting in a highly promising low-temperature PEALD process at 60 °C. The new precursors were synthesized in the multigram scale and thoroughly characterized by thermogravimetric analyses, revealing high and tunable volatility reflected by appreciable vapor pressures and accompanied by thermal stability. Typical ALD growth characteristics in terms of linearity, saturation, and a broad ALD window with constant growth of 1.06 Å cycle^-1 in the temperature range of 60-240 °C render this process very promising for fabricating high-purity smooth HfO₂ layers. For the first time, NAP-XPS surface studies on selected HfO₂ layers are reported upon exposure to reactive H₂, O₂, and H₂O atmospheres at temperatures of up to 500 °C revealing remarkable stability against degradation. This can be attributed to the absence of surface defects and vacancies. On the basis of these promising results, PEALD-grown HfO₂ films were used as dielectric layers in the MIS capacitor device fabrication exhibiting leakage current densities less than 10^-7 A cm^-2 at 2 MV cm^-1 and permittivities of up to 13.9 without postannealing.