Lateral double diffused metal oxide semiconductor device and manufacturing method thereof

A manufacturing method of a lateral double diffused metal oxide semiconductor (LDMOS) device, comprising:

• providing a substrate with a first conductive type;
• forming with a second conductive type a drift region on the substrate;
• forming an isolation oxide region on the drift region to define an operation region, wherein the operation region is located in the drift region;
• forming an oxide region on the drift region in the operation region having a first thickness by same process steps which form the isolation oxide region;
• defining a second oxide region in the oxide region by a mask layer;
• forming the second oxide region in the oxide region having a second thickness by an etching process, wherein a first oxide region is formed, which is a remaining not-etched portion of the oxide region, wherein the second oxide region is directly connected to the first oxide region in a lateral direction, wherein the second thickness is less than the first thickness;
• removing the mask layer;
• forming a gate on the drift region in the operation region, which overlays at least part of the second oxide region and part of the first oxide region, including:
• forming a dielectric layer on the drift region, which is directly connected to the second oxide region in the lateral direction, wherein the second oxide region separates the dielectric layer and the first oxide region from each other;
• forming a stack layer on the dielectric layer;
• and
• forming a spacer layer over a side wall of the stack layer;
• forming a body region with a first conductive type in the drift region, and part of the body region is beneath the gate;
• forming a source with the second conductive type in the body region, wherein the spacer layer is located between the source and the stack layer from a top view;
• and
• forming a drain with the second conductive type in the drift region, which is located between the first oxide region and the isolation oxide region;
• wherein the first oxide region, the second oxide region, and the isolation oxide region are local oxidation of silicon (LOCOS) structures;
• wherein the isolation oxide region, the drain, the first oxide region, the second oxide region, and the dielectric layer are sequentially connected in the lateral direction.