In this study, various charge trapping mechanisms and their effects on the endurance of n- and p-type HfO2-based FeFETs, integrated within GlobalFoundries 28 nm bulk high-k metal gate (HKMG) technology are examined. The device’s endurance is impaired due to pronounced interface degradation and charge injection into the Metal-Ferroelectric-Insulator-Semiconductor (MFIS) gate stack caused by the high interfacial field stress. By analyzing threshold voltage shifts under both bipolar and unipolar cycling, as well as bipolar endurance cycling for “non-ferroelectric” samples with diminishing remanent polarization levels, the study reveals the critical role of polarization switching in endurance degradation. The findings highlight the deterioration of the gate stack and specifically of the interface of FeFETs upon bipolar cycling which strongly affects the electrical characteristics and causes increased electron trapping in n-type-FeFETs and hole trapping in p-type FeFETs. This effect is particularly pronounced for each device's low threshold-voltage (LVT) state and is intensified by polarization switching. The study's results contribute to a deeper understanding of the charge trapping phenomena in HfO2-based FeFETs and their impact on device performance and reliability.