Electroacoustic biosensors are widely studied nowadays as they can provide a complete and cheap solution for the real time detection of virus, or different diseases, in a very small liquid sample (e.g. blood, urine, saliva). One of these electroacoustic sensors are based on Solidly Mounted Resonators (SMRs). These devices have proven their potential as biosensors but never been optimized from their acoustic reflector point of view. Most of the optimizations were focused on the deposition of tilted piezoelectric materials to excite an acoustic shear mode, the one needed to operate in liquid. The objective of this thesis was to perform a full optimization of the SMR technology for its use as biosensor.