  Here we report the successful growth of MoSe2 on single layer hexagonal boron
nitride (hBN) on Ru(0001) substrate by using molecular beam epitaxy. We
investigated the electronic structures of MoSe2 using scanning tunneling
microscopy and spectroscopy. Surprisingly, we found that the quasi-particle gap
of the MoSe2 on hBN/Ru is about 0.25 eV smaller than those on graphene or
graphite substrates. We attribute this result to the strong interaction between
hBN/Ru which causes residual metallic screening from the substrate. The surface
of MoSe2 exhibits Moir\'e pattern that replicates the Moir\'e pattern of
hBN/Ru. In addition, the electronic structure and the work function of MoSe2
are modulated electrostatically with an amplitude of ~ 0.13 eV. Most
interestingly, this electrostatic modulation is spatially in phase with the
Moir\'e pattern of hBN on Ru(0001) whose surface also exhibits a work function
modulation of the same amplitude.
