With　the　aim　of　understanding　the　effect　of　creep　defects　in　the　gamma＇　phase　on　the　creep　resistance,　the　atomic　structure　and　elemental　segregation　behavior　of　stacking　faults　(SFs),　three　types　of　SF　interactions　and　antiphase　boundaries　(APBs)　in　a　Co-Al-W-based　single-crystal　superalloy　crept　at　1000　degrees　C/137　MPa　up　to　1.0%　strain　were　investigated.　Both　superlattice　intrinsic　and　extrinsic　stacking　faults　(SISF　and　SESF)　were　observed　in　the　gamma＇　precipitates,　and　the　interactions　of　such　faults　had　different　configurations.　Both　V-　and　T-like　configurations　can　be　composed　of　SISF-SISF,　SISF-SESF　and　SESF-SESF　interactions,　while　the　X-like　configuration　was　only　observed　to　be　composed　by　SISF-SISF　interaction.　The　strengthening　effect　and　mechanism　of　such　SF　interactions　on　the　creep　resistance　are　discussed　based　on　their　density　and　formation　mechanism.　W　elemental　segregation　was　present　along　the　SISFs　and　SESFs.　In　contrast,　only　the　gamma　forming　element　Co　was　enriched　near　the　leading　partial　dislocations　(LPDs)　of　the　SISFs/SESFs,　stair-rod　dislocations　and　APBs.　The　rate　limiting　step　of　the　expansion　of　the　SFs　was　estimated　to　be　the　drag　effect　induced　by　the　Co　diffusion.　In　addition,　the　local　phase　transformation　from　the　L1(2)　to　A1　structure　at　the　intersection　of　SFs　was　mainly　attributed　to　the　Co　supersaturation　and　aided　by　wetting　phenomenon　from　the　APB.　(C)　2020　Acta　Materialia　Inc.　Published　by　Elsevier　Ltd.　All　rights　reserved.