If this breaker is supplying a single receptacle, than the receptacle has to be rated the same as the branch circuit that supplies it (210.21(B)(1).
210.21(B)(3) Table - shows that a 15 ampere rated receptacle can be supplied by a 20 ampere circuit. Provided there is more than one receptacle on that circuit.
Remember that a 20 ampere circuit requires a 12 AWG conductor. See 240.4(D).
[This message has been edited by PCBelarge (edited 09-18-2004).]