  B20-type MnSi is the prototype magnetic skyrmion material. Thin films of MnSi
show a higher Curie temperature than their bulk counterpart. However, it is not
yet clear what mechanism leads to the increase of the Curie temperature. In
this work, we grow MnSi films on Si(100) and Si(111) substrates with a broad
variation in their structures. By controlling the Mn thickness and annealing
parameters, the pure MnSi phase of polycrystalline and textured nature as well
as the mixed phase of MnSi and MnSi1.7 are obtained. Surprisingly, all these
MnSi films show an increased Curie temperature of up to around 43 K. The Curie
temperature is likely independent of the structural parameters within our
accessibility including the film thickness above a threshold, strain, cell
volume and the mixture with MnSi1.7. However, a pronounced phonon softening is
observed for all samples, which can tentatively be attributed to slight Mn
excess from stoichiometry, leading to the increased Curie temperature.
