Semiconductor nanowire devices having cavity spacers and methods of fabricating cavity spacers for semiconductor nanowire devices are described. For example, a semiconductor device includes a plurality of vertically stacked nanowires disposed above a substrate, each of the nanowires including a discrete channel region. A common gate electrode stack surrounds each of the discrete channel regions of the plurality of vertically stacked nanowires. A pair of dielectric spacers is on either side of the common gate electrode stack, each of the pair of dielectric spacers including a continuous material disposed along a sidewall of the common gate electrode and surrounding a discrete portion of each of the vertically stacked nanowires. A pair of source and drain regions is on either side of the pair of dielectric spacers.