In this study, DP (Double Patterning) and DPS (Double Patterning with Spacer) were comprehensively compared through word line layout of 50nm node product, and special focus was put on the assessments of layout discontinuity zones through experimental validation. In conventional flash manufacturing, the lithographic proximity effect and etch loading effect around the array-gap zones have been inherent characteristics to be addressed. For DP process, apart from the overlay error induced pattern displacement and CD non-uniformity, the cross-coupling effects between adjacent features around the array-gap zones by two photo and two etch steps have further complicated the process optimization, therefore careful exploration was carried out to indicate the challenges on process optimization. The DPS can maintain good resultant CD uniformity of dense array through precisely programmed exposure CD and spacer thickness, it may also keep away from the proximity around array-gap zones. But, the second exposure is necessary for trimming the unwanted patterns and delineating the peripheral patterns. In purpose of trimming the unwanted patterns at array-gap zone in the 2nd exposure, the overlay registration will account for the CD control of boundary lines as well as the defectivity around this area.