It can be observed that MM elements’ sensitivity to the amplitude of 3-nm LER features is a function of the optical properties of the material, spatial period of LER features, and pitch, height, CD, and SWA of the Si fins. The average deviations of the MM elements in the wavelength range of 250 to 800 nm obtained for a model with a 3-nm LER amplitude and varying feature parameters with respect to the undisturbed reference structure are seen in Fig. 6(a). It is observed that a high-frequency LER features (spatial period of 3 nm) has a higher impact on the calculated optical spectra of MM elements compared to a low-frequency LER (spatial period of 14 nm). Also, the sensitivity to LER increases with the height of the patterns and as the CD to pitch ratio increases. For example, the sensitivity of MM elements to LER decreases when the height of Si fins is reduced to 40 nm and the pitch value is increased to 56 nm as seen in Figs. 6(a) and 6(b). The sensitivity of MM elements to 3-nm LER features is least for the 28-nm pitch line-space patterns in which the optical properties of PMMA (photoresist material) are used instead of the optical properties of Si and is observed only in the wavelength region of 250 to 380 nm. Hence, LER inspection in photoresist line-space patterns must be carried out using a light source with ultraviolet (UV) and vacuum UV (VUV) spectral range. The highest sensitivity of MM elements to LER is observed when the SWA value is near 90 deg, i.e., when Si fins are straight and not trapezoidal. In addition, it is observed that the MM24 off-diagonal MM element has the highest sensitivity to LER for all the 28-nm pitch patterns, but on the diagonal element, MM34 is the most sensitive MM element for the Si fins with a pitch of 56 nm for data generated at a 60 deg azimuthal angle. The spectral distribution of the MM elements, more sensitivity to certain feature parameters in different wavelength regions, and different optical responses of all MM elements to change in feature parameters are helpful in separating the impact of various feature parameters like CD, height, and LER on the optical spectra during the solution of the inverse problem approach of scatterometry.