Abstract: A method of forming a semiconductor device includes depositing a target metal layer in an opening. Depositing the target metal layer comprises performing a plurality of deposition cycles. An initial deposition cycle of the plurality of deposition cycles comprises: flowing a first precursor in the opening, flowing a second precursor in the opening after flowing the first precursor, and flowing a reactant in the opening. The first precursor attaches to upper surfaces in the opening, and the second precursor attaches to remaining surfaces in the opening. The first precursor does not react with the second precursor, and the reactant reacts with the second precursor at a greater rate than the reactant reacts with the first precursor.