type grade area 210 functions to form the n type ions with a low concentration outside of the source drain so as to reduce the dope dose of a pn junction and to increase the breakdown voltage of the junction the eighth photoresist layer is removed in the present embodiment the n type ions injected to form the n type grade area 210 are phosphorus ions the ions are injected at a dosage of 1 u00d7 1013 cm2 and energy of 80 kev u02dc 100 kev as illustrated in fig1 a ninth photoresist layer not illustrated is spin coated on the n epitaxial layer the local oxidation of silicon locos isolation area 204 and the gates 208 a and 208 b and an nsink area pattern is defined in the vdmos transistor area ii after the exposure and development processes n type ions are injected into the epitaxial layer between the local oxidation of silicon locos isolation area 204 and the adjacent gate 208 b in the vdmos transistor area ii along the nsink area pattern using the ninth photoresist layer as a mask to form an nsink area 212 wherein the nsink area 212 is communicated with the n buried layer area 201 moreover the nsink area 212 functions to lead a drain electrode out of the substrate thereby improve the dope dose as much as possible and reducing the series resistance the ninth photoresist layer is removed in the present embodiment the n type ions injected to form the nsink area 212 are phosphorus ions the ions are injected at a dosage of 1 u00d7 1015 cm2 and energy of 300 kev u02dc 400 kev as illustrated in fig1 a tenth photoresist layer not illustrated is spin coated on the.