ABSTRACT Optical metrology techniques are essential for process control of gate formation process steps from lithography to the dielectric, spacers, gate and straining layer deposition in sub-90nm technology nodes. Traditionally, optical metrology is based on the measurement of periodic lines or hole arrays us ing a spectroscopic ellipsometer or reflectometer, collecting data across a wide wavelength spectrum at a single angle of incidence. In this paper, we present results of measurements on periodic Poly-Si gate line arrays using laser based Focused Beam Scatterometry (FBS), illuminating at 3 discrete laser wavelengths while data is collected over an angle of incidence range from 45° to 65°. Accuracy, repeatability, and tool-to-tool matching results for the poly-Si gate line arrays are discussed. Comparison with the CD-SEM and cross-section TEM result for measurement/mode ling accuracy is also presented. KEYWORDS Scatterometry, critical dimension, metr ology, OCD, Focused Beam Scatterometry