Although some years have passed since the discovery of the ferroelectric phase in HfO₂ and ZrO₂ and their solid solution system Hf_xZr₁−_xO₂, the details of the emergence of this phase are still under investigation. Surface energy contribution, dopant inclusion, residual stress, electric field, and oxygen vacancies have been proposed and studied as potential factors that can influence the phase stabilization. In this work, Hf_xZr₁−_xO₂ layers with different Hf/Zr ratios are deposited via atomic layer deposition (ALD) and physical vapor deposition (PVD) and the amount of oxygen that is supplied during deposition is varied. Results are compared for the two deposition techniques for undoped HfO₂ layers. Electrical and structural analysis for the atomic layer-deposited films with different Zr contents and O₂ contents is then performed and the reliability of the films when integrated into capacitors is addressed. The results are correlated to the composition of the layers and a model for layer crystallization is suggested.