Note that a continuation application has to be filed before the patenting or abandonment of or termination of proceedings on his or her earlier non provisional application, based on an earlier filed patent application, wherein there is no new disclosure. However, a additional set of features can be claimed.
However, a divisional application is filed on a scenario, if a patent application lacks unity of invention.Generally such application is filed upon issuance of restriction requirement or upon asked by the examiner stating that application lacks unity of invention.Even a divisional application has to be filed before the patenting or abandonment of or termination of proceedings on his or her earlier non provisional application, based on an earlier filed patent application.
Hence, one cannot file for continuation or divisional application to claim additional features because the parent application has been granted.
http://www.invntree.com/blogs/patent-protection-for-improvements-made-over-your-previously-filed-patent-application.
There is a another way out wherein the applicant may surrender the issued patent and refile the original application to correct the defect for example, if he fails to claim the full scope of the invention. However, he can file an application with broaden claims within 2 years from the date of the patent application being grant.Please note that no new matter can be disclosed in the application being re -filed.