The application discloses a threshold value adjustable vertical
double diffusion metal oxide semiconductor field effect transistor, which comprises a drift region, a
body region formed in the drift region from the upper surface of the drift region downwards, a
gate oxide layer formed on the upper surfaces of the drift region and the
body region, and a PN junction composite
polysilicon gate formed on the upper surface of the
gate oxide layer and composed of a first type polysilicon and a second type polysilicon, wherein the second type polysilicon covers all surfaces of the first type polysilicon except the bottom, and the
vertical projection of the PN junction junction boundary formed by the first type polysilicon and the second type polysilicon is located in the
body region in the channel region. When the
transistor is turned on, the PN junction composite
polysilicon gate is in a
reverse bias state, and the
threshold voltage is raised by affecting the inversion process of the body region through the junction
electric field. The application realizes the raising of the
threshold voltage of the device without weakening other performances of the device, and does not change the core
gate oxide process and need to cooperate with a groove structure.