Micro- and nano-electronic devices based on metal-oxide-metal (MOM) and complementary metal-oxide-semiconductor (CMOS) systems are the basis of modern technology. Over many decades, scaling down of transistor- and memory-device dimensions have led to exponential advances in computing power. This scaling has also led to the replacement of SiO₂ with higher dielectric constant materials, such as HfO₂. However, in spite of decades of perfection, oxides used in CMOS devices, including SiO₂ and HfO₂, are prone to  many field-induced reliability issues^[1]. Here, we present the results of multi-scale modelling which link the physical processes responsible for the field induced degradation of amorphous (a-) HfO₂ with the characteristics of time-dependent dielectric breakdown (TDDB), such as temporal evolution of current through the oxide and Weibull plots of TDDB. Model parameters characterizing the creation of oxygen vacancies and the electron tunneling process are calculated using Density Functional Theory (DFT), employing a hybrid density functional. The vacancy-generation model is based on previous work, which shows that electrons trap into deep, intrinsic states in a-HfO₂^[2] . The trapping of electrons into these states facilitates the production of vacancies by lowering the activation energy for vacancy-interstitial pair generation^[3]. It is found that subsequent trapping of electrons at vacancies also facilitates the production of additional vacancies. We calculate a range of parameters associated with these defects and reactions and use this information to parameterize a device level simulation in the Ginestra code^[4]. Effects such as TAT, Fowler-Nordheim tunneling, heat generation and vacancy generation et cetera are all included. This allows us to simulate the time evolution current through a TiN/HfO₂/TiN subjected to electrical stress, accounting for how stress-induced carrier injection and vacancy-interstitial pair generation are inter-related and ultimately affect the oxide properties. The results show that the trap based model agrees well with experiments on the field-induced degradation of HfO₂. We also gain an insight into the formation of the percolation pathway from the spatial distribution of generated vacancies. This also confirms the Joule feedback mechanism, in which so-called hard breakdown is caused by local heating around a percolation pathway, leading to a catastrophic increase and current and generation of vacancies.