The　interface　quality　between　the　gate　dielectric　and　germanium　(Ge)　channel　plays　a　crucial　role　for　Ge　MOSFETs.　The　impact　of　different　interface　passivation　techniques　on　the　total　ionizing　dose　(TID)　effect　of　Ge　pMOSFET　with　enclosed-layout　and　Al2O3/TiN　gate-stack　is　experimentally　investigated　under　different　bias　conditions.　The　N-passivation　and　O-passivation　of　Ge　pMOSFETs　are　realized　by　nitrogen-plasma-passivation　(NPP)　and　rapid-thermal-oxidation,　respectively.　Negative　threshold　voltage　(Vth)　shift　and　positive　Vth　shift　are　observed　for　devices　irradiated　under　on-state　and　TG-state,　respectively,　which　are　partially　due　to　negative　bias　temperature　instability　(NBTI)　and　positive　bias　temperature　instability　(PBTI)　stresses.　The　NBTI　and　PBTI　effects　are　evaluated　to　obtain　＂pure＂　Vth　shifts　induced　by　TID　irradiation.　The　O-passivated　Ge　pMOSFETs　show　larger　pure　radiation-induced　Vth　shifts　than　N-passivated　devices,　which　is　attributed　to　less　irradiation-induced　border　trap　density　in　the　N-based　interfacial　layer　(IL)　than　the　O-based　IL.　Therefore,　N-based　IL　is　more　suitable　for　Ge　MOSFET　than　the　O-based　IL　from　a　perspective　of　radiation　hardness.　The　results　may　provide　interface　material-design　guideline　for　radiation-hardened　and　high-performance　Ge　MOSFET　fabrication.