Manufacturing method of low-threshold voltage NMOS tube with total dose resistance

The invention discloses a manufacturing method of a low-threshold-voltage NMOS (N-channel Metal Oxide Semiconductor) tube with total dose resistance, and belongs to the field of semiconductor process manufacturing. The method comprises the following steps: firstly, forming an active region of an NMOS tube device, isolating the active region through an STI (Shallow Trench Isolation) silicon shallow slot, reinforcing the bottom and the side wall of the STI silicon shallow slot by adopting a conventional reinforcing method, then carrying out HDP (High Density Plasma) filling, then forming a body region of the NMOS device, and performing subsequent process. For an NMOS tube with low threshold voltage, impurity injection is carried out twice in a body region to form two depth distributions: high-energy injection determines the depth of the body region of the NMOS tube, and middle-energy anti-punch-through injection meets the withstand voltage requirement of the NMOS tube. According to the method, optimization and