Ge　has　been　an　alternative　channel　material　for　the　performance　enhancement　of　complementary　metal-oxide-semiconductor　(CMOS)　technology　applications　because　of　its　high　carrier　mobility　and　superior　compatibility　with　Si　CMOS　technology.　The　gate　structure　plays　a　key　role　on　the　electrical　property.　In　this　paper,　the　property　of　Ge　MOSFET　with　Al2O3/GeOx/Ge　stack　by　ozone　oxidation　is　reviewed.　The　GeOx　passivation　mechanism　by　ozone　oxidation　and　band　alignment　of　Al2O3/GeOx/Ge　stack　is　described.　In　addition,　the　charge　distribution　in　the　gate　stack　and　remote　Coulomb　scattering　on　carrier　mobility　is　also　presented.　The　surface　passivation　is　mainly　attributed　to　the　high　oxidation　state　of　Ge.　The　energy　band　alignment　is　well　explained　by　the　gap　state　theory.　The　charge　distribution　is　quantitatively　characterized　and　it　is　found　that　the　gate　charges　make　a　great　degradation　on　carrier　mobility.　These　investigations　help　to　provide　an　impressive　understanding　and　a　possible　instructive　method　to　improve　the　performance　of　Ge　devices.