We studied the electrical and structural properties of Cu-Ni alloy thin films and narrow trenches prepared by the pulse electroplating method. The plating conditions and use of an appropriate organic additive introduced variations in the Ni content that modulated the electrical resistivity. We observed that the grain growth mechanism strongly depended on the uniformity of the seed layers. Gap-fill on narrow trench patterns was demonstrated. We also observed the diffusion of Ni to the surface layers both in the thin films and in narrow trenches when annealed at high temperatures. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.020112esl] All rights reserved.