A bulk wave resonator that includes an aluminum nitride film containing scandium on a substrate, a first electrode disposed on one surface of the aluminum nitride film containing scandium, and a second electrode disposed on the other surface of the aluminum nitride film containing scandium. The aluminum nitride film containing scandium includes a portion acoustically isolated from a top surface of the substrate. The first electrode overlaps the second electrode with the aluminum nitride film containing scandium interposed therebetween. The overlap forms a piezoelectric vibrating portion. The scandium content of the aluminum nitride film containing scandium is 5 atomic percent or more and 43 atomic percent or less when Sc and Al of the aluminum nitride film containing scandium constitute 100 atomic percent.