  In the inflationary cosmology it occurs frequently that the inflaton field is
trapped in a local, transient minimum with non-zero vacuum energy. The
difficulty regarding the curvature perturbation produced during such a stage is
that classically the inflaton does not move so that the comoving hypersurfaces
are not well defined at linear order in the scalar field perturbation. In this
paper, assuming a mechanism of trapping which resembles a high temperature
correction to the potential, we explicitly calculate for the first time the
resulting power spectrum of the curvature perturbation by evaluating the
quantum two-point correlation function directly. The spectrum is steeply blue
with the spectral index n_R = 4.
