The characteristics of one-port aluminum nitride (AlN) Lamb wave resonators utilizing the lowest-order symmetric mode with electrically open, grounded, and floating bottom electrode configurations are theoretically and experimentally investigated in this paper. Finite element analysis is performed to take an insight into the static capacitance characteristics of the AlN Lamb wave resonators with various bottom surface conditions. Without sacrificing the transduction efficiency, the floating bottom electrode is capable of reducing the static capacitance in the AlN thin plate and then promotes an efficient improvement in the effective coupling coefficient (k²_eff). In addition, in comparison with the grounded bottom electrode, the employment of the floating bottom electrode offers simple fabrication processes for the micromachined Lamb wave resonators. Experimentally, the AlN Lamb wave resonators without the bottom electrode exhibit an average loaded quality factor (Q) as high as 2676 at the series resonance frequency, but a low average k²_eff of 0.19%. On the contrary, the Lamb wave resonators with the electrically floating bottom electrode show the largest average k²_eff up to 1.13% among the three topologies but a low average loaded Q of 800 at the series resonance frequency. In contrast to the floating bottom electrode, the Lamb wave resonators with the electrically grounded bottom electrode show a smaller average k²_eff of 0.78% and a similar average loaded Q of 758 at the series resonance frequency.

Microacoustic resonators made on suspended continuous membranes of LiNbO ₃ were recently shown to have very strong coupling and low losses at ≥5 GHz, suitable for high‐performance filter design. Employing these simple resonator structures, the authors have designed, fabricated, and measured a 4.7 GHz bandpass ladder‐type filter having 1 dB mid‐band loss and 600 MHz bandwidth to address the 5G Band n79 requirements. The filter is fabricated on a monolithic substrate using standard i‐line optical lithography and standard semiconductor processing methods for membrane release, starting with commercially available ion‐sliced wafers having 400 nm thickness crystalline LiNbO ₃ layers. The filter is well‐matched to a 50 Ω network and does not require external matching elements. Through accurate resonator engineering using our finite element method software filter design environment, the passband is spurious‐free, and the filter provides better‐than 30 dB rejection to the adjacent WiFi frequencies. This filter demonstrates the performance and scalable technology required for high‐volume manufacturing of microacoustic filters >3.5 GHz.