SAW devices for frequency filters are increasingly required to have high performance in future mobile communications. The coupling factors K2 for Rayleigh-type SAW (RSAW) on ScAlN film/high velocity substrate structures can be enhanced by introducing polarization-reversal structure into the ScAlN film. However, the growth of polarization-reversal ScAlN films with high crystal orientation would be very difficult. In this study, the Sezawa mode RSAWs on layered structures consisting of ScAlN films with floated intermediate electrode layer / high velocity substrates were analyzed by using Farnell and Adler's SAW propagation analysis and finite element method. We found that the K2 values of the Sezawa modes were enhanced by inserting the floated intermediate electrode layer without using polarization reversal structure, which were higher than those of the polarization-reversal ScAlN films/high velocity substrates. The enhancement of K2 would be due to the improvement of the SAW energy concentration at the ScAlN film surface.