Be really careful about this: yes, many/most PhD programs grant a Master’s degree along the way, but it is often incidental to the overall program. In many funded PhD program, finishing with a Master’s is an off-ramp for students who aren’t going to make it through the PhD process- a consolation prize if you will, and not something you would plan to do.
Each PG program is specific about their policies on Masters and PhDs, so research is smart- but do it closer to time, as policies can change. For example, until very recently, the horticulture group at Cornell had a straight MS or PhD choice, but they have now restructured it along the lines @merc81 mentions. It is easily 3 years too soon for the OP to be thinking about this level of grad school detail.