Surface acoustic wave resonator, acoustic wave filter, and multiplexer

A surface acoustic wave resonator comprising:

• a substrate having piezoelectricity;
• an IDT electrode on the substrate;
• and
• reflectors sandwiching the IDT electrode in a propagation direction of an acoustic wave;
• wherein
• the IDT electrode is defined by only one IDT electrode;
• the IDT electrode and the reflectors each include a plurality of electrode fingers extending in a direction crossing the propagation direction of the acoustic wave and being in parallel or substantially in parallel to one another;
• and
• when
• a distance between a k-th electrode finger and a (k+1)-th electrode finger in the propagation direction of the acoustic wave is defined as a k-th electrode finger pitch, where k is an integer larger than or equal to 2;
• in a (k−1)-th electrode finger, the k-th electrode finger, and the (k+1)-th electrode finger adjacent to each other, a value obtained by dividing a difference between the k-th electrode finger pitch and a section average electrode finger pitch, which is an average of the (k−1)-th electrode finger pitch and the (k+1)-th electrode finger pitch, by an overall average electrode finger pitch, which is an average pitch of overall electrode fingers which the IDT electrode or the reflectors have, the IDT electrode or the reflectors including the adjacent three electrode fingers, is defined as a pitch deviation ratio of the k-th electrode finger;
• and
• a distribution of the pitch deviation ratio obtained by calculating the pitch deviation ratio of the k-th electrode finger for all of the electrode fingers which the IDT electrode or the reflectors include, the IDT electrode or the reflectors including the adjacent three electrode fingers, is defined as a histogram of the pitch deviation ratio;
• at least one of the IDT electrode and the reflectors has a standard deviation of the pitch deviation ratio in the histogram larger than or equal to about 0.2%.