This paper presents a thin-film piezoelectric-on-substrate (TPoS) micro-resonator with a resonant frequency around 770MHz. This high frequency operation has been enabled through reducing inter-electrode gap. After optimization of geometrical design and fabrication process, resonators was measured showing an electromechanical coupling coefficient k t 2 of 2.2%, a high quality factor Q m of 1460 and a low motional resistance (R m ≈ 21 Ω). Experimental data have shown good agreement with theoretical computations.