A stacked-die oscillator package includes an oscillator circuit die having inner bond pads, and outer bond pads, and a bulk acoustic wave (BAW) resonator die having a piezoelectric transducer with a first and second BAW bond pad on a same side coupled to a top and bottom electrode layer across a piezoelectric layer. A first metal bump is on the first BAW bond pad and a second metal bump is on the second BAW bond pad flip chip bonded to the inner bond pads of the oscillator circuit die. A polymer material is in a portion of a gap between the BAW and oscillator circuit die.