  Primordial black holes (PBHs) could be formed if large perturbations are
generated on small scales in inflation. We study a toy inflation model with a
local minimum. The curvature perturbations are enhanced when the inflaton
passes through the local minimum, with more efficient amplification rate than
that of quasi-inflection point inflation, leading to the production of PBHs on
small scales. The PBHs could comprise the total dark matter in the mass window
$10^{16}$--$10^{20}$g.
