To improve the fill factor (FF) over 0.7, the following research has been performed, such as 1) our sulfurization after selenization (SAS) process condition for the Cu(InGa)(SeS)(2) (CIS)-based absorber formation is fixed to attain the open-circuit voltage (V(oc)) of over 0.630 V/cell, 2) thickness of a double buffer structure with both Zn(O,S,OH)(x) deposited by a chemical-bath deposition (CBD) technique and intrinsic ZnO deposited by a metal-organic chemical vapor deposition (MOCVD) technique is adjusted by optimizing the series resistance (R(s)) and the shunt resistance (R(sh)), 3) post-deposition annealing in vacuum after CBD is applied to reduce the hydroxide (OH) concentration, and 4) narrower pattern-2 and -3 scribe lines contribute to make the interconnect width less than 200 mu m and to keep the short-circuit current density (J(sc)) over 34 mA/cm(2). As the result, for the first time a FF of over 0.7 has been achieved in our CIS research and development (R&D) since FY1993. This is the biggest contributor to achieve our FY2007 milestone of 15% efficiency with aperture area larger than 800 cm(2). We have achieved this milestone in the form of a laminated module. (C) 2008 Published by Elsevier B.V.