  We demonstrate a unified scenario for neutrino mass, baryon asymmetry, dark
matter and inflation. In addition to a fermion triplet for the so-called
minimal dark matter, we extend the standard model by three heavy fields
including a scalar singlet, a fermion triplet and a fermion singlet/Higgs
triplet. The heavy scalar singlet, which is expected to drive an inflation, and
the dark matter fermion triplet are odd under an unbroken $Z_2^{}$ discrete
symmetry, while the other fields are all even. The heavy fermion triplet offers
a tree-level type-III seesaw and then mediates a three-body decay of the
inflaton into the standard model lepton and Higgs doublets with the dark matter
fermion triplet. The heavy fermion singlet/Higgs triplet not only results in a
type-I/II seesaw at tree level but also contributes to the inflaton decay at
one-loop level. In this scenario, the type-I/II seesaw contains all of the
physical CP phases in the lepton sector and hence the CP violation for the
non-thermal leptogenesis by the inflaton decay exactly comes from the imaginary
part of the neutrino mass matrix.
