In any of the sciences and (more limitedly since this isn’t my specific area) humanities I don’t know of a single program that requires a masters to apply for the doctorate. The masters is usually the result of someone leaving the doctoral program after coursework is complete but before having completed a large enough body of research to be considered ABD (all but dissertation). It could be different perhaps in other fields. There are definitely masters specific programs - MBA and public health both come to mind but at least for public health I don’t know of a program that would require the MPH for admission to a PhD program.