  Gamma-ray bursts (GRBs) that emit photons at GeV energies form a small but
significant population of GRBs. However, the number of GRBs whose GeV-emitting
period is simultaneously observed in X-rays remains small. We report gamma-ray
observations of GRB 110625A using Fermi's Large Area Telescope (LAT) in the
energy range 100 MeV to 20 GeV. Gamma-ray emission at these energies was
clearly detected using data taken between 180s and 580s after the burst, an
epoch after the prompt emission phase. The GeV light curve differs from a
simple power-law decay, and probably consists of two emission periods.
Simultaneous Swift/XRT observations did not show flaring behaviors as in the
case of GRB 100728A. We discuss the possibility that the GeV emission is the
synchrotron self-Compton radiation of underlying ultraviolet flares.
