The shear horizontal (SH) mode on the SiO2/Al/LiNbO3 structure is studied because of its sufficient electromechanical coupling factor (K2) and good temperature coefficient of frequency (TCF). The authors proposed a method of suppressing the spurious response of the Rayleigh mode and the transverse mode for narrow duplex gap applications. For the narrow duplex gap application, the SiO2 thickness must be increased to achieve good TCF characteristics. However, another spurious response appears near the fast shear wave with increasing SiO2 thickness. In this paper, we discuss the suppression mechanism of the spurious response near the fast shear wave.