vention is still further characterized in that at least one of such metals as Fe, Zr, Al Cr, Mn, Rh, Cu, V, W, U and Sn is contained as an impurity in said piezoelectric substrate to provide increased conductivity of said piezoelectricsubstrate.The invention is also characterized in that said piezoelectric substrate is made of LiTaO.sub.3.The invention is further a surface-mount SAW device which c