We report studies on the role of a ZnTe buffer in determining the crystalline phase of MBE-grown MnSe1-xTex alloy thin films. It was found that MBE growth of MnSe and MnTe directly onto a zincblende GaAs substrate usually result in their corresponding stable phases, which are rocksalt and hexagonal, respectively. A set of zincblende MnSe1-xTex alloy thin films with Te composition covering from 0.27 to 1 were fabricated on zincblende ZnTe buffer layers. We have addressed the lattice distortion issue due to thin film effect for these films. A combination of several structural characterizations demonstrates that a perfect lattice matched MnSe1-xTex/ZnTe heterostructure can indeed be realized. The results of this study pave the way for realizing a double-barrier MnSe1-xTex/ZnTe/MnSe1-xTex resonant tunneling diode structure with perfect lattice match as a candidate for a promising THz emitter.