Abstract: A metal interconnect structure includes at least a pair of metal lines, a cavity therebetween, and a dielectric metal-diffusion barrier layer located on at least one portion of walls of the cavity. After formation of a cavity between the pair of metal lines, the dielectric metal-diffusion barrier layer is formed on the exposed surfaces of the cavity. A dielectric material layer is formed above the pair of metal lines to encapsulate the cavity. The dielectric metal-diffusion barrier layer prevents diffusion of metal and impurities from one metal line to another metal line and vice versa, thereby preventing electrical shorts between the pair of metal lines.