An　ozone-based　plasma　pretreatment　was　proposed　to　reduce　the　oxygen　vacancy　and　unstable　germanium　(Ge)　suboxide　(GeOx)　at　lower　interface　of　interfacial　layer　(IL).　With　higher　oxidizing　ability　of　ozone　and　lower　plasma　damage　in　process,　the　formation　of　unstable　GeO(x　)at　lower　interface　of　IL　can　be　effectively　suppressed.　The　devices　with　a　mixed　hydrogen　and　ozone　plasma　(MHOP)　pretreatment　exhibit　an　ultrathin　equivalent　oxide　thickness　(EOT)　of　0.57　nm,　a　fairly　acceptable　gate　leakage　current　density　of　3　x　10(-3)A/cm(2),　lower　interface　trap　density　of　10(11　)cm(-2)eV(-1),　and　fewer　border　traps　inGe　MOS　capacitor.　Also,　a　higher　driver　current　of　1.4　mA,　a　lower　subthreshold　swing　(SS)　of　113　mV/dec,　and　higher　ON/OFF　current　ratio　of　3.2　x　10(3　)for　Ge　MOSFET　can　be　achieved　with　an　MHOP　treatment.