The design, fabrication and experimental investigation of 21MHz MEM Bulk Lateral Resonators (BLR) on 1.5 mu m Silicon-On-Insulator (SOI) Fragmented Membranes with 100nm air-gaps are reported(#). Quality factors as high as 33'000 are measured under vacuum at room temperature, with 20V DC bias and low AC-power. The influence of temperature on the resonance frequency and quality factor is studied and discussed from 80K and 380K. A very high quality factor of 182'000 and a motional resistance of 165k Omega, are reported at 80K. The paper shows that high-quality factor MEM resonator can be integrated on partially-depleted thin SOI, which demonstrates the possibility of making full-integrated hybrid MEM-CMOS integrated circuits for future communication applications.