In semiconductor devices, fine patterning can cause structural instability because of intrinsic compressive stress. We studied one such instability phenomenon, out-of-plane wiggling of a patterned structure with mask–dielectric ridges, to improve the yield of these highly miniaturized devices. Our simple continuum approach uses dimensionless parameters to control the bifurcation threshold of ridge wiggling. Coupled with modeling the etching process, our approach revealed the onset of buckling, agreeing well with experimental data. To study the influence of the ridge width and the elastic substrate on buckling stress and deformation, we performed numerical analyses using a finite element method (FEM).