This chapter follows directly from the last chapter the reader is referred to that chapter for an introduction to implantation damage. This chapter focuses on changes in the microstructure that occur upon annealing ion implanted silicon. A brief review of the solid phase epitaxial growth of implantation induced amorphous layers is presented followed by a section focusing on the formation of extended defects upon annealing. The types of defects that form are presented in detail followed by a discussion of the defects most commonly seen for the most important dopants. The implantation steps used in ULSI processing can be divided into three topics including low energy implants for shallow junction formation as well as the use of higher energy implants for the formation of retrograde wells and the formation of gettering layers. The role of extended defects in each of these cases is presented. A brief description of more novel uses of ion implantation for ion beam synthesis and lifetime tailoring is reviewed. Finally SiC is finding wide scale application in high power devices. Therefore, a review of implant related defects in SiC is presented.