  We study a generalized superconformal model that gives rise to a subcritical
regime of D-term hybrid inflation. Formulating the model in a Jordan frame, the
effective potential of the subcritical regime is derived in the Einstein frame.
It turns out the inflaton-waterfall field dynamics leads to various types of
inflaton potential. Consequently the tensor-to-scalar ratio is found to range
from $10^{-4}$ ($10^{-3}$) to $0.1$ for get 60 (50) $e$-folds before the end of
inflation.
