a detailed description of the present invention will be further given below in detail with reference to the accompanying drawings and embodiments . for ease of description , the thickness of layers and regions is amplified in the drawings , and the depicted sizes are not the actual sizes . although the drawings do not completely accurately reflect the actual sizes of a device , they give a complete reflection of the relative positions of the regions and the constituting structures , particularly the up - and - down and adjacency relationships between the constituting structures . the following embodiments of the present invention shall not be considered as being limited to the specific shapes of the regions shown in the drawings , but include the obtained shapes , such as variations due to the manufacture . fig2 to fig1 illustrate a technical process of an embodiment of a method 1 for manufacturing a split - gate power device according to the present invention . the process includes the following specific steps . firstly , as shown in fig2 , a substrate epitaxial layer 301 of a first doping type is formed above a drain region 300 of the first doping type , a first insulating film 400 is formed above the substrate epitaxial layer 301 , a first photoetching process is performed to define the position of a control gate groove , and the first insulating film 400 is etched to form an opening 410 of the first insulating film in the first insulating film 400 . the material of the first insulating film 400 may be silicon oxide or silicon nitride , and may also be a stacked layer of silicon oxide and silicon nitride , for example , an insulating film of an ono structure , including a first oxide layer , a second nitride layer , and a third oxide layer that are sequentially stacked . next , as shown in fig3 , the substrate epitaxial layer 301 is etched by using the first insulating film 400 as a mask to form a control gate groove 500 in the substrate epitaxial layer 301 . in the etching process of this step , lateral etching may be added to form lateral recesses of the control gate groove 500 below the first insulating film 400 , the lateral width of the lateral recess being a . then , as shown in fig4 , a second insulating film 302 is formed on the surface of the control gate groove , and a first conductive film 600 is deposited , the first conductive film 600 at least filling the lateral recesses at the two sides of the control gate groove 500 and below the first insulating film 400 . in the present embodiment , the first conductive film 600 fills the control gate groove 500 . the material of the second insulating film 302 is preferably silicon oxide , and the material of the first conductive film 600 is polysilicon or metal . next , as shown in fig5 , a part of the first conductive film 600 above the first insulating film 400 is etched away , and the first conductive film 600 is further etched along the edge of the opening 410 of the first insulating film to form control gates 303 with a lateral width of a at the two sides of the control gate groove , wherein the lateral width a of the control gates 303 should satisfy the requirement for subsequent formation of control gate contact holes , and if the lateral width a of the control gates 303 is too small , the formation of the control gate contact holes may be affected . as shown in fig6 , the exposed second insulating film 302 is etched away , a third insulating film is deposited and etched - back to form third insulating film dielectric layers 401 on exposed side walls of the control gates 303 , and the substrate epitaxial layer 301 is etched along the edges of the third insulating film dielectric layers 401 to form a split - gate groove , the material of the third insulating film dielectric layer 401 being preferably silicon nitride . in the above step , the split - gate groove is formed by self - aligned etching of the substrate epitaxial layer 301 using the third insulating film dielectric layers 401 as a mask , and because the etching of the control gate groove and the split - gate groove only uses one mask plate for etching the control gate groove , the complexity and cost of device processing are reduced . next , as shown in fig7 , a fourth insulating film 304 is formed on the surface of the split - gate groove , the material of the fourth insulating film 304 being preferably silicon oxide . then , as shown in fig8 , the third insulating film dielectric layers 401 are etched away , and a fifth insulating film 305 is formed on the exposed surfaces of the control gates 303 , the material of the fifth insulating film 305 being preferably silicon oxide . then , as shown in fig9 , a second conductive film is deposited to cover the formed structure and is etched - back to form a split - gate 306 in the split - gate groove , the surface of the split - gate 306 being slightly lower than the surface of the substrate epitaxial layer 301 , and the material of the split - gate 306 being preferably doped polysilicon . next , as shown in fig1 , the first insulating film 400 is etched away , and a thin oxide layer 307 is formed by oxidization for restoring the surface of the substrate epitaxial layer 301 ; ion implantation of a second doping type is performed to form a channel region 308 in the substrate epitaxial layer 301 , the bottom of the channel region 308 being preferably at the bottom position of the control gate groove ; a second photoetching process is performed to define the position of a source region ; ion implantation of the first doping type is performed to form a source region 309 in the substrate epitaxial layer 301 ; a sixth insulating film 310 is deposited to cover the formed structure , a third photoetching process is performed to form contact hole patterns , and the sixth insulating film 310 is etched to form contact holes ; and finally ion implantation of the second doping type is performed and a metal layer 311 is deposited to form ohmic contact . the material of the sixth insulating film 310 is silicate glass , boro - phospho - silicate glass , or phospho - silicate glass . the second doping type and the first doping type in the present invention are opposite doping types , that is , if the first doping type is n - type doping , the second doping type is p - type doping ; or if the first doping type is p - type doping , the second doping type is n - type doping . finally , fourth photoetching is performed , and the metal layer is etched to respectively form a source electrode , a control gate electrode , and a split - gate electrode . preferably , the drain region 300 may be formed in the substrate epitaxial layer 301 by ion implantation after the source electrode , the control gate electrode , and the split - gate electrode are formed , and then a metal layer is deposited to form a drain electrode . fig1 to fig1 illustrate a technical process of an embodiment of a method 2 for manufacturing a split - gate power device according to the present invention . the process includes the following specific steps . firstly , according to the processes shown in fig2 and fig3 , a control gate groove 500 is formed in a substrate epitaxial layer 301 , a second insulating film 302 is formed on the surface of the control gate groove , and a first conductive film 600 is deposited to cover the formed structure , the first conductive film 600 at least filling lateral recesses at two sides of the control gate groove 500 and below a first insulating film 400 , as shown in fig1 . the material of the second insulating film 302 is preferably silicon oxide , and the thickness of the second insulating film 302 ranges from 10 nm to 50 nm . the material of the first conductive film 600 is polysilicon or metal . next , as shown in fig1 , a part of the first conductive film 600 above the first insulating film 400 is etched away , and the first conductive film 600 is further etched along the edge of an opening 410 of the first insulating film to form control gates 303 with a lateral width of a at the two sides of the control gate groove , the exposed second insulating film 302 is etched , and the substrate epitaxial layer 301 is etched along the edges of the control gates 303 by using the first insulating film 400 as a mask to form a split - gate groove . then , as shown in fig1 , a third insulating film 304 is deposited , and the third insulating film 304 covers the surfaces of the control gates 303 and the surface of the split - gate groove . the material of the third insulating film 304 is preferably silicon oxide . the thickness of the third insulating film 304 shall be not smaller than half of the width of the split - gate groove , and is preferably 200 nm to 1000 nm . next , as shown in fig1 , a second conductive film is deposited to cover the formed structure and is etched - back to form a split - gate 306 in the split - gate groove , the surface position of the split - gate 306 being slightly lower than the surface position of the substrate epitaxial layer 301 , and the material of the split - gate 306 being preferably doped polysilicon . finally , as shown in fig1 a and fig1 b , the exposed third insulating film 304 and the first insulating film 400 are etched away , and a thin oxide layer 307 is formed by oxidization for restoring the surface of the substrate epitaxial layer 301 ; ion implantation of a second doping type is performed to form a channel region 308 in the substrate epitaxial layer 301 , the bottom of the channel region 308 being preferably at the bottom position of the control gate groove ; a second photoetching process is performed to define the position of a source region ; ion implantation of a first doping type is performed to form a source region 309 in the substrate epitaxial layer 301 ; a fourth insulating film 310 is deposited to cover the formed structure , the material of the fourth insulating film 310 being silicate glass , boro - phospho - silicate glass , or phospho - silicate glass ; a third photoetching process is performed to form contact hole patterns , and the fourth insulating film 310 is etched to form contact holes ; and then ion implantation of the second doping type is performed and a metal layer 311 is deposited to form ohmic contact . fig1 a illustrates an ohmic contact structure at source electrode contact holes , and fig1 b illustrates an ohmic contact structure at control gate electrode contact holes . the fourth insulating film 304 between the split - gate and the control gates of the split - gate power device obtained by the present invention is thick , and even if the control gate electrode contact holes are located on the fourth insulating film 304 due to alignment deviation , the device reliability is not be affected , and therefore , the impact on device reliability caused by alignment deviation of the control gate electrode contact holes is reduced , and the process difficulty is lowered . the contents not specifically described in the specific embodiments of the present invention are known in the art and may be implemented with reference to known techniques . the present invention has been verified via repeated tests , and satisfactory test results are achieved . the embodiments mentioned in the detailed description above are provided to support the technical concept of the method for manufacturing a split - gate power device according to the present invention , and are not intended to limit the scope of protection of the present invention . any equivalent modification or variations made based on the present technical solution following the technical concepts of the present invention , all fall within the scope of protection of the present invention .