Fabrication of via contacts having dual silicide layers

A method is provided for fabricating a via contact structure contacting a single-crystal semiconductor diffusion region at a top surface of a substrate. In such method, a first layer is formed in contact with the diffusion region at the top surface, the first layer consisting essentially of a silicide of a first metal. A dielectric region is formed to overlie the first layer. An opening is etched in the dielectric region extending through the first layer to the diffusion region. A second layer is formed to line the opening, the second layer including a second metal. Thereafter, a conductor is deposited within the opening over the second layer, and the substrate is heated to cause the second metal to form a silicide at the top surface.