157nm lithography is expected to be the lithography choice for the 100nm-technology node, which is scheduled to be in full-production in 2003. However, due to 157nm photons being strongly absorbed by commonly used polymeric organic materials, a completely new class of material (containing F and Si-O) will be needed for 157nm Single Layer Resist (SLR) system. It is expected that the 157nm SLR system development will take greater than 3 years, which the industry will barely have, until the projected 2003 production schedule. In an attempt to fill the gap and to provide working resist system, using thin (<100nm)films of existing resist materials along with inorganic thin hardmask/BARC films is an attractive approach. In this paper, we report the optical constants (n % k at 157nm as well as 193nm and 248nm) of various thin film hardmask/BARC candidate materials (SixNyHz, SixOyNz, SixCyCVD and TixNyPVD films) measured by VUV-VASE. The films' atomic compositions, determined by RBS/HFS, were varied by controlling feed gas flow rates in order to vary the optical behavior. However, we limited our study within the low process temperature PE-CVD and PVC films due to our intention of using these films along with LowK(2.7approximately equals 2.0) dielectric materials. In addition, we will also report the optical constants of two types of LowK materials (PE-CVD OSG film and Spin- On/Cure low-density organosilicate dielectrics by JSR.) The data is, then, used to optimize the physical properties (n & k) and utilized to determine suitable hardmask/BARC material for 157nm exposure using Prolith II simulation. The results containing property of these hardmask/BARC candidate films and our optimization analysis along with the first successful pattern transfer feasibility demonstration into realistic substrate material (poly-Si) using ultra thin resist (currently existing) at 157nm optical lithography are reported.