  The collapse of sufficiently large closed domain wall produced during second
order phase transition in the vacuum state of a scalar field can lead to the
formation of black hole. The origin of domain walls with appropriate size and
energy density could be a result of evolution of an effectively massless scalar
field at the inflational epoch. We demonstrate that in this case the situation
is valued when there are compact domains of less favorable vacuum surrounded by
a sea of another vacuum. Each domain has a surface composed of vacuum wall that
stores a significant amount of energy, and can collapse into the black hole.
This offers the way of massive primordial black holes formation in the early
Universe.
