Surface acoustic wave (SAW) resonators are the modern equivalents of the old bulk crystal resonators, used for high-Q frequency filtering, or very accurate frequency sources. A conventional resonator consists of a transmitting/receiving transducer, bounded from both sides by grid reflectors, creating a “Fabry-Perot” cavity structure. A major disadvantage of conventional resonators is their large dimension, which makes them inconvenient for integrated applications. In order to overcome this size limitation, new types of microresonators were designed and tested. These guided SAW resonators are able to guide and control the propagating component of the acoustic energy upon them, almost without losses. Based on theoretical calculations, two kinds of such devices were developed, namely, a corrugated waveguide filter and a microresonator structure. The main component in each of those devices is a metallic ΔV/V channel, which confines the propagating wave underneath and small, x-direction, transverse, short metallic strips in order to obtain periodic perturbations. Based on the “coupled mode theory,” it was found that by using such periodic perturbations, a complete Fabry-Perot reflecting mirror for surface acoustic waves can be realized. The reflection coefficient of such a micrograting mirror is almost total and its performances are similar to the conventional resonators. [This work was supported by the Israeli Ministry of Communications.]