  The scalar meson $D_{s0}^*(2317)$ is found 37(17)MeV below DK threshold in a
lattice simulation of the $J^P=0^+$ channel using, for the first time, both DK
as well as $\bar sc$ interpolating fields. The simulation is done on $N_f=2+1$
gauge configurations with $m_\pi\simeq 156 $MeV, and the resulting
$M_{D_{s0}^*}-\tfrac{1}{4}(M_{D_s}+3M_{D_s^*})=266(16)$ MeV is close to the
experimental value 241.5(0.8)MeV. The energy level related to the scalar meson
is accompanied by additional discrete levels due to DK scattering states. The
levels near threshold lead to the negative DK scattering length $a_0=-1.33(20)$
fm that indicates the presence of a state below threshold.
