  We consider the extension of the Standard Model (SM) with a light inflaton
where both unitarity problem in Higgs inflation and vacuum instability problem
are resolved. The linear non-minimal coupling of the inflaton to gravity leads
to a significant kinetic mixing between the inflaton and the graviton such that
perturbative unitarity is restored up to Planck scale. We show the correlation
between unitarity scale and inflationary observables in this model and discuss
how the effective Higgs inflation appears.
