  We discuss a minimal extension of the Standard Model (SM) where a single real
scalar field serves as both inflaton and dark matter. The corresponding
Lagrangian contains the renormalizable interactions of the inflaton field.
Quantum effects generally induce a non-minimal coupling to gravity which
facilitates inflation consistent with the PLANCK constraints. A large fraction
of the inflaton quanta produced after inflation must be converted into the SM
radiation reheating the Universe and the rest remains dark matter today. We
consider thermal and non-thermal production of inflaton dark matter. In the
non-thermal case, we take into account collective effects with the help of
lattice simulations. Combining analytic and numerical results with the
unitarity consideration, we find that the inflaton dark matter model is viable
only in the thermal case where the inflaton mass is near half the Higgs mass.
