A power MOS
field effect transistor with polysilicon field plate and a manufacture method thereof are characterized in that a terminal protection structure of the periphery of an active region of the MOS
field effect transistor is improved in the following aspects: 1. a P<-> trap of the periphery of edged unit cells of a unit
cell array is directly treated as a field limiting ring; 2. a field limiting ring P<-> area, a
cut-off ring P<-> area and a P<-> trap of the unit
cell array are treated as the same manufacturing layer which is formed by P-shaped
doping simultaneously; 3. field
oxygen is omitted, the structure of the field plate is changed in composition and composed by a grid silica layer and polysilicon; 4. the polysilicon in the field plate is treated as a
barrier layer injected with P-shaped
impurity ions, and the field limiting ring P<-> area, the
cut-off ring <-> area and the P<-> trap of the unit
cell are formed directly; 5. N-shaped
doping is carried out after P-shaped
doping, thus causing upper parts of the field limiting ring P<-> area, the
cut-off ring P<-> area and the P<-> trap of the unit cell array have an N<+> area. The power MOS
field effect transistor with polysilicon field plate and a manufacture method thereof of the invention have the advantages of saving the photoglith plate of the active region, the photoglith plate of the field limiting ring and the photoglith plate with three
layers injected in the active region, on the premise of guaranteeing performance of products, reducing times of photoetching, reducing manufacture cost greatly, which are suitable for manufacturing the power MOS
field effect transistor with low cost on a large scale.