Similar to the Rayleigh SAW, the Surface Transverse Wave (STW) device uses input and output transducers to launch and receive the propagating acoustic surface wave. However, the differences are two-fold. First, the STW device uses a metal grating structure to trap the propagating wave to the surface of the substrate. Without the grating, the wave propagates at a slight angle into the bulk of the substrate resulting in attenuation of the wave. Secondly, the displacement of the propagating STW is in the plane of the substrate with no vertical component of displacement.

Since there is no vertical component of displacement, the STW could theoretically be used for liquid-based applications. In a practical sense, use as a liquid-based sensor is very unlikely. Placing water on the surface of the device will dielectrically short out the IDT electrodes preventing the excitation of the STW. Isolation of the IDTs from the liquid has been tried with various types of packaging (i.e. passivation coatings or o-ring sealed flow cavity), but this usually results in significant losses in the device characteristics. For this reason, the STW is typically only used for gas sensing.