there is described a semiconductor device which has an isolation region , the isolation region being polished by means of chemical - and - mechanical polishing , and which prevents occurrence of variations in a finished state of active regions even in a case where a large isolation area is present . an isolation region for separating active regions is formed on a semiconductor wafer . an annular dummy pattern is formed in an inactive region of greater than a predetermined size , so as to surround the isolation region . an isolation region is ensured between the active regions surrounding the inactive region and the dummy pattern .