This　paper　describes　two　models　that　are　related　to　the　defect　of　gate　oxide　and　one　thermal　resistance　model　of　semiconductor　devices　to　evaluate　chip　life.　With　CMOS　IC　technology　scaling,　the　conventional　TDDB　model　cannot　provide　the　necessary　accuracy　for　calculation　and　prediction.　And　the　reliability　of　thin　gate　oxides　is　also　one　of　the　most　important　problems　in　CMOS　integrated　circuits.　Thus　the　development　of　CMOS　TDDB　model　is　very　important.