A branching 1 filter has an antenna terminal 3 which receives signal waves and disturbance waves, a transmission filter 11 which is connected to the antenna terminal 3, a reception filter 13 which is connected to the antenna terminal 3 and receives a portion of the signal waves and has, as a passband, a frequency range higher than a passband of the transmission filter 11, and a disturbance wave resonator which is connected to the antenna terminal 3 and to the ground and positioned closer to the antenna terminal 3 side than the transmission filter 11 and the reception filter 13. The disturbance wave resonator 15 is connected to antenna terminal 3 at a position closer to the antenna terminal 3 side than the transmission filter 11 and the reception filter 13. A resonance frequency of the disturbance wave resonator 15 is within a frequency range smaller than the passband of the transmission filter and includes a frequency range of the disturbance waves.

SAW element has a substrate; an IDT having a first comb-shaped electrode and a second comb-shaped electrode located on an upper surface of the substrate; and a capacitance element located on the upper surface of the substrate. The capacitance element has a first counter electrode connected to the first comb-shaped electrode and a second counter electrode connected to the second comb-shaped electrode and facing the first counter electrode across a third gaps. The direction from the first counter electrode through the third gaps toward the second counter electrode is a reverse direction from the direction from the first comb-shaped electrode through the gaps toward the second comb-shaped electrode. If it is assumed that the gap and width of the gap are d.sub.i and w.sub.i, and the gap and width of the third gap are D.sub.j and W.sub.j, the following formula holds:
0<(W.sub.j/D.sub.j.sup.2)<2(w.sub.i/d.sub.i.sup.2).

The present invention relates to a surface acoustic wave filter device with floating units. The surface acoustic wave filter device comprises a piezoelectric substrate, at least one interdigitated transducer configuration and at least one floating unit. The interdigitated transducer configuration comprises a plurality of interdigitated transducer units disposed on the piezoelectric substrate. The floating unit is disposed between adjacent interdigitated transducer units, and covers partial region of adjacent interdigitated transducer units to reduce the BAW scattering of the surface acoustic wave filter device, and can be used to improve the amplitude and phase balances of the surface acoustic wave filter devices.