STFR were fabricated on the floating membrane which was formed by SOI-micromachining process. The floating membranes having a thickness range of $3{sim}15{mu}m$ could be simply formed by micromachining the directly-bonded and thinned SOI substrate. The STFR device fabricated on the $15{mu}m$-thick membrane showed resonance frequency of fr = 1.65 GHz, coupling coefficient of Keff2 = 2.4 %, and series and parallel quality factors of Qs = 91.7 and Qp = 87.7, respectively.