  We have studied a leptogenesis scenario in the framework of the minimal
seesaw model with tri/bi-maximal mixing. Usually, at least one of the elements
in the Dirac mass matrix is fixed to be zero, for example, we denote it by
$b_2=0$. We have pointed out that the absolute value of the CP asymmetry has
several minimums and maximums with non-zero $b_2$. Thus one can expect that
more rich phenomena, such as an enhanced leptogenesis, are hidden in the $b_2
\neq 0$ space.
