“…The use of SiO 2 as a compensating material has been shown to work in both surface acoustic wave devices 16 and film bulk acoustic resonators 17 and has been previously suggested 14,18,19 for silicon micromachined resonators. Negative valued temperature coefficients 9,10 result in material softening such that the stiffness, and thus frequency, of silicon resonators decreases with increasing temperature.…”