A semiconductor device includes a substrate, a dielectric structure, a top metal layer and a bonding structure. The dielectric structure is disposed on the substrate. The top metal layer is disposed in the dielectric structure. The bonding structure is disposed on the dielectric structure and the top metal layer. The bonding structure includes a silicon oxide layer, a silicon oxy-nitride layer, a conductive bonding layer and a barrier layer. The silicon oxide layer is disposed on the dielectric structure. The silicon oxy-nitride layer covers the silicon oxide layer. The conductive bonding layer is disposed in the silicon oxide layer and the silicon oxy-nitride layer. The barrier layer covers a sidewall and a bottom of the conductive bonding layer.