The invention provides an anti-EMI super-junction VDMOS device and a preparation method thereof. The device is provided with a composite
dielectric layer consisting of an
oxide layer (SiO2), a semi-insulating
polycrystalline silicon layer (SIPOS) and an
oxide layer (SiO2) in a super-junction drift region, wherein the
oxide layer isolates a drift region from the SIPOS layer, the lower portion of the SIPOS layer is connected with the device drain
electrode metal, and the upper portion of the SIPOS layer is connected with the device source
electrode metal. When the device is in a turn-off state, the composite
dielectric layer assists in depletion of the super junction drift region, so that the
doping concentration of the drift region can be greatly improved, and the phenomenon that the withstand
voltage is reduced due to mismatch between a super junction P column and an N column can be relieved; and in the switching process of the device, because the SIPOS is directly connected with the source
electrode and the drain electrode of the device, the output
capacitance Coss of the device is greatly improved, the switching oscillation is reduced, and thus the
voltage oscillation dV / dt failure possibility and the EMI
noise of the device are reduced.