We report a novel method to fabricate zero-space microlenses without light loss for CMOS image sensor. Classical microlenses for CMOS image sensor, adopted for achieving high quality images by providing appropriate propagation and collection of light onto photo diode, are typically formed by patterning and thermal flowing process of square type photo resist array sequentially. In that process, sufficient spaces between microlenses must be maintained to avoid merging by keeping an isolated microlens for in arrayed lenses during thermal flowing process. In order to remove the spaces between microlenses, we have developed a dual step patterning process in conjunction with optimal thermal flowing process developed for obtaining optimum microlens shape. The characteristics of zero-space microlenses without light loss were also demonstrated comparing with classical microlenses.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.