The　impact　of　y-ray　exposure　on　Hot-Carrier　effects　of　65nm　bulk　Si　NMOSFETs　and　the　dependence　on　device　geometry　is　experimentally　investigated.　Experimental　results　show　that　stress-induced　degradation　on　irradiated　devices　is　severer　than　un-irradiated　devices.　Besides,　the　geometry　dependence　of　degradation　is　illustrated:　the　narrower　the　device　the　larger　the　stress-induced　degradation,　which　is　attributed　to　the　radiation-induced　trapped　charges　in　STI.　The　results　indicate　that　the　reliability　issue　of　MOS　devices　is　more　challenging　in　harsh　environment　due　to　the　synergetic　effect　of　TID　and　HCI.　©　2018　IEEE.