  We present results from the Suzaku observation of the microquasar GRS
1915+105 performed during the 2005 October multiwavelength campaign. The data
include both stable state (class \chi) and limit-cycle oscillation (class
\theta). Correct interstellar absorption as well as effects of dust scattering
are fully taken into account in the spectral analysis. The energy spectra in
the 2-120 keV band in both states are all dominated by strong Comptonization of
disk photons by an optically thick (\tau ~7-10) and low temperature (T_e ~2-3
keV) hybrid plasmas containing non-thermal electrons produced with 10-60% of
the total power input. Absorption lines of highly ionized Fe ions detected
during the oscillation indicate that a strong disk wind is developed. The
ionization stage of the wind correlates with the X-ray flux, supporting the
photoionization origin. The iron-K emission line shows a strong variability
during the oscillation; the reflection is strongest during the dip but
disappears during the flare. We interpret this as evidence for "self-shielding"
that the Comptonizing corona becomes geometrically thick in the flare phase,
preventing photons from irradiating the outer disk. The low-temperature and
high luminosity disk emission suggests that the disk structure is similar to
that in the very high state of canonical black hole binaries. The spectral
variability during the oscillation is explained by the change of the disk
geometry and of the physical parameters of Comptonizing corona, particularly
the fractional power supplied to the acceleration of non-thermal particles.
