This　paper　investigates　the　effects　of　different　passivation　layers　(PVLs)　on　the　electrical　performance　and　reliability　of　amorphous　indium　gallium　zinc　oxide　(a-In-Ga-ZnO)　thin　film　transistors　(TFTs).　By　rational　design,　the　fabricated　a-InGaZnO　TFT　with　hafnium　oxide　and　aluminumoxide　(HfO2/Al2O3)　dual　PVLs　exhibits　a　field-effect　mobility　of　13.5　cm2/Vs,　low　sub　threshold　swing　of　0.32　V/decade,　and　especially,　small　threshold　voltage　shifts　of　0.5　(-0.6)　V　and　1.1　(-1.2)　V　under　positive　(negative)　gate　bias,　and　light　illumination　stress　at　the　relative　humidity　of　40%.　Furthermore,　the　a-In-Ga-ZnO　TFTswith　HfO2/Al2O3　dual　PVLs　maintain　reasonable　mobility　and　electrical　performance　even　exposure　to　ambient　condition　for　up　to　four　months.　This　enhanced　stability　is　attributed　to　the　presence　of　high-quality　HfO2/Al2O3　dual　PVLs,　which　not　only　could　suppress　the　photodesorption,　reduce　the　total　trap　density　and　subgap　photoexcitation　behavior,　but　also　protect　the　channel　from　environmental　effects.　Thus,　the　rational-designed　HfO2/Al2O3　dual　PVLs　passivated　a-In-Ga-ZnO　TFTs　with　superior　reliability　represent　a　great　step　toward　the　achievement　of　long-term　reliable　zinc　oxide-based　oxide　TFTs.　©　1963-2012　IEEE.