A semiconducting device with a dual sidewall spacer and method of forming are provided. The method includes: depositing a first spacer layer over a patterned structure, the first spacer layer having a seam propagating through a thickness of the first spacer layer near an interface region of a surface of the substrate and a sidewall of the patterned structure, etching the first spacer layer to form a residual spacer at the interface region, where the residual spacer coats less than the entirety of the sidewall of the patterned structure, depositing a second spacer layer on the residual spacer and on the sidewall of the patterned structure not coated by the residual spacer, the second spacer layer being seam-free on the seam of the residual spacer, and etching the second spacer layer to form a second spacer coating the residual spacer and coating the sidewall of the patterned structure not coated by the residual spacer.