A semiconductor device includes a metal gate. The semiconductor device further includes a first dielectric layer extending along a sidewall of the metal gate and including at least one of a plurality of cross-linked first silicon-oxygen-silicon backbones or a plurality of cross-linked first silicon-carbon-silicon backbones. The semiconductor device further includes a second dielectric layer extending along the first dielectric layer. The second dielectric layer extending along the first dielectric layer includes at least one of a plurality of cross-linked second silicon-oxygen-silicon backbones or a plurality of cross-linked second silicon-carbon-silicon backbones.