For decades, negative bias temperature instability (NBTI) has been on the forefront of transistor reliability concerns. Electrically detected magnetic resonance (EDMR) has provided significant insight regarding NBTI's atomic scale mechanisms in conventional (planar) metal oxide semiconductor field effect transistors (MOSFETs). More recently, however, tri-gate MOSFETs have become the prevailing devices in integrated circuity. In this study, we have investigated the atomic scale mechanisms of the NBTI in tri-gate MOSFETs. Also, for the first time, a direct comparison of EDMR responses is made between similarly processed planar and tri-gate FETs. We have done this by utilizing two EDMR techniques: spin dependent charge pumping and spin dependent trap assisted tunneling (SDTAT). Our results indicate both similarities and differences in the atomic scale mechanisms of NBTI in planar and tri-gate devices. Our work also introduces a new EDMR technique for the observation of NBTI defects generated within gate dielectrics: SDTAT.