schottky and p-n junction in varactor diode

According to a book about microwave and solid circuit I have read, the key structure of a varactor diode is its PN junction. When PN junction is reverse biased, we can make use of its potential barrier capacitance. In a word: a varactor diode is a PN junction device actually.

But I find another term: schottky varactor diode, in some other books. We know schottky barrier is a metal-semiconductor junction which is different from p-n junction, as I know.

Since "a varactor diode is a PN junction device actually" , how to explian "schottky varactor diode"?

varactor diode is P-N junction device operated in reverse bias.
schottky diode is basically metal-semiconductor junction which will have low barrier and fast recovery time.
under revers bias the depletion region should be sufficient to have wider capacitance range.
so P-n juntion i.e semi-semi (not metal-semi) under reverse bias will have wider capacitance range.

Schottky diode when operated under reverse bias ( any diode in general) will behave like varactor but the tuning range is very limited then the regular vari-cap.

in this context schottky diode works as schottky varactor diode.