U(1)'-extended MSSM with/without CP violation.<br>
Unlike the MSSM, the EWPT can be strong first order without a light stop.<br>
In such a case, the singlet-like Higgs bosons and the charged Higgs bosons<br>
play an important role. It is found that at least two Higgs bosons should be<br>
less than 300 GeV for the strong first order phase transition.<br>
Depending on the charged Higgs boson mass, the lightest Higgs boson can be<br>
as large as 220 GeV. It is also found that the CP violating phase in the Higgs sector<br>
do not weaken the strength of the first order EWPT.<br>