The　degradations　of　parameter　and　mechanism　produced　by　different　p-base　region　diffusion　temperatures　in　split-gate-trench　MOSFET　(SGT-MOS)　with　approximate　threshold　voltage　is　investigated　in　this　paper　through　Sentaurus　TCAD.　In　SGT-MOS,　the　threshold　voltage　(Vth)　does　not　decrease　monotonously　with　the　increase　of　the　diffusion　temperatures　under　the　gate-controlled　range.　A　snap-back　of　threshold　voltage　occurs　when　the　PN　junction　between　p-base　region　and　n-drift　region　reaches　the　crescent　shaped　gate　polysilicon　manufactured　by　early　wet　etching　process　at　a　certain　temperature,　and　further　temperature　rise　will　make　the　threshold　voltage　decrease.　Although　the　Vth　of　the　devices　with　PNJ　in　uniform　gate　region　and　crescent　gate　region　are　similar,　the　degradations　of　the　on-state　resistance　and　capacitance　of　SGT-MOS　occurs,　which　reduces　the　switching　frequency　of　the　device.　©　2021　ACM.