Asymptotic tails of massive scalar fields in a Schwarzschild background

We investigate the asymptotic tail behavior of massive scalar fields in a Schwarzschild background. It is shown that the oscillatory tail of the scalar field has the decay rate of t(-5/6) at asymptotically late times, and the oscillation with the period 2 pi /m for the field mass m is modulated by the long-term phase shift. These behaviors are qualitatively similar to those found in a nearly extreme Reissner-Nordstrom background, which are discussed in terms of a resonant backscattering due to the space-time curvature.