Method for making LDMOS device and LDMOS device

A method for making an LDMOS device, comprising:

• forming a well doped region in a substrate;
• forming a gate oxide on the substrate, wherein there is an overlap region between the bottom of the gate oxide and an upper surface of the well doped region;
• forming a polysilicon gate on the gate oxide, wherein the polysilicon gate and the gate oxide form a step structure, the gate oxide forms a bottom step of the step structure, and a lateral length of the gate oxide is greater than a lateral length of the polysilicon gate;
• performing drift region ion implantation at least two times to form a drift region in the substrate, wherein the drift region covers the well doped region and the bottom of the gate oxide, a doping concentration distribution in the drift region is nonuniform in a lateral direction and in the at least two times of drift region ion implantation, there is a difference in energy between at least two times of drift region ion implantation, and ions need to pass through the step structure and an exposed substrate during the drift region ion implantation;
• and
• performing heavily doped ion implantation, to separately form a source terminal and a channel lead-out terminal in the well doped region and to form a drain terminal in the drift region.