Abstract: A chemical sensor includes a piezoelectric support (1) capable of supporting a shear horizontal wave provided on its surface with an electrode (2,3). The sensor is characterized in that the surface of the piezoelectric support (1) including the region bearing the electrode (2,3) is covered by a layer of dielectric material (9) of thickness 0.5 to 20 microns. The piezoelectric support (1) is preferably a single crystal. The dielectric layer (1) may be of, for example, silicon dioxide or a suitable polymer, and preferably has a thickness of between 0.5 and 5 .mu.m.