The　super　junction　(SJ)　drift　is　used　in　internal　transparent　collector　IGBT.　The　influences　of　position　of　local　carrier　lifetime　region,　local　carrier　lifetime,　and　buffer　layer　doping　level　on　the　devices＇　trade-off　characteristics　have　been　simulation　studied.　The　results　show　that　for　given　local　carrier　liftetime,　the　turn-off　losses　may　have　a　valley　value　E-offmin.　The　higher　local　carrier　lifetime　is,　the　higher　E-offmin　will　be.　Several　factors　are　at　work.　Competition　effects　for　excess　carrier　extraction　through　reverse　biased　super　junction　and　forward　biased　collector　may　be　one　reason.　Infinite　excess　carrier　recombination　velocity　in　local　carrier　lifetime　control　region　leads　to　the　back-emitter　injection　efficiency　gamma(e)　be　no　less　than　certain　value.　In　addition;　increasing　buffer　layer　doping　level　appropriately　could　win　better　trade-off　and　wider　trade-off　range.