Yes. For many years now, when I have read the specifications for above the range microwaves, they have all required their own circuit. In my many years of practice as an electrician, electrical contractor, I have sometimes seen that some unqualified electrician has removed an old range exhaust fan and used that wire, but it was not dedicated.
This is not good. So, yes, you do need the above the range microwave on its own circuit breaker from the electrical panel.