Transverse leakage is a significant issue in Surface Acoustic Wave (SAW) filters and duplexers that utilize 42°YX-lithium tantalate(42LT) substrates. This leakage increases insertion loss, reduces bandwidth, and flattens the roll-off, negatively impacting the performance of SAW devices. In this paper, we propose a wider dummy structure to suppress transverse leakage. The effectiveness of this structure is verified through finite element method (FEM) simulations. Furthermore, we extend this wider dummy structure to Band 40 and Band 41 SAW filters. Experimental results demonstrate that the structure enables SAW devices to achieve lower insertion loss, broader bandwidth, and steeper roll-off characteristics. Additionally, this novel structure has the potential to be applied to other SAW filter bands.