  We study the heavy-light mesons in a relativistic model, which is derived
from the instantaneous Bethe-Salpeter equation by applying the Foldy-Wouthuysen
transformation on the heavy quark. The kernel we choose is based on scalar
confining and vector Coulomb potentials, the transverse interaction of the
gluon exchange is also taken into account in this model. The spectra and wave
functions of $D$, $D_s$, $B$, $B_s$ meson states are obtained. The spectra are
calculated up to the order of $1/m_Q$, and wave functions are treated to
leading order.
