  We study the inflation due to the D-flat direction of an extra $U(1)$. This
scenario is a hybrid of a right-handed sneutrino inflaton scenario and a gauge
non-singlet inflaton scenario. The inflaton is a gauge non-singlet field which
induces a right-handed neutrino mass spontaneously through an extra $U(1)$
D-flat direction. This right-handed neutrino mass can explain the solar
neutrino problem. The reheating temperature resulting from the decay of the
coherent oscillation of the right-handed sneutrino is sufficiently high so that
the baryogenesis based on the lepton number asymmetry can be applicable. We
also discuss the realistic model building.
