Methods for forming interconnects in microfeature workpieces, and microfeature workpieces having such interconnects are disclosed herein. In one embodiment, a method of forming an interconnect in a microfeature workpiece includes forming a hole extending through a terminal and a dielectric layer to at least an intermediate depth in a substrate of a workpiece. The hole has a first lateral dimension in the dielectric layer and a second lateral dimension in the substrate proximate to an interface between the dielectric layer and the substrate. The second lateral dimension is greater than the first lateral dimension. The method further includes constructing an electrically conductive interconnect in at least a portion of the hole and in electrical contact with the terminal.