The invention provides a manufacturing method of a
trench IGBT. The method comprises the following steps: providing a substrate and dividing into an active region and a terminal structure region; opening a window of a
protection ring in the terminal structure region; through an
ion implantation and
diffusion technology, forming the device
protection ring in the substrate; forming
field oxide on a surface of the substrate and completing an active region definition; forming a groove
hard mask layer and a
photoresist layer on the surfaces of the substrate and the
field oxide, and imaging the
photoresist layer;
etching the groove
hard mask layer and exposing the substrate; depositing a sidewall
protection layer on the surface of the substrate and performing etchback, forming protection side walls on sidewalls of two sides of the groove
hard mask layer and growing a
thermal oxide layer on the surface of the substrate; taking the groove hard
mask layer and the protection side walls as the hard
mask so as to successively etch the
thermal oxide layer and the substrate and forming a groove in the substrate, wherein the
thermal oxide layer which is on a top of the groove extends between the protection side walls and the substrate so as to form a
beak. According to the invention, generation of a
closed angle of the groove top can be avoided. Grid leakage failure and a reliability problem caused by the
closed angle can be prevented.