After electrode patterning on an electrode forming surface of a piezoelectric substrate 2 (FIG. 1(b)), a conductor layer is formed on an electrode non-forming surface of the piezoelectric substrate 2 (FIG. 1(c)). After forming the conductor layer, the conductor layer formed on the other surface is removed (FIG. 1(f)) after at least one step (FIG. 1(e)), and thereafter, dicing for separation into elements and mounting on a mounting substrate are carried out. By removing all the conductor layer on the other surface of the piezoelectric substrate, the out-of-passband attenuation and isolation performance can be significantly improved.