Method of fabricating semiconductor device having a trench structure penetrating a buried layer

A method of fabricating a lateral-diffusion-metal-oxide-semiconductor (LDMOS) device, comprising:

• providing a semiconductor substrate;
• forming a buried layer in the semiconductor substrate;
• forming a well having a first conductivity type in the semiconductor substrate, wherein the well is disposed on the buried layer;
• forming a first trench structure in the well, wherein the first trench structure extends into the buried layer and a bottom surface of the first trench structure not passing through and higher than a bottom surface of the buried layer;
• forming a second trench structure in the semiconductor substrate, wherein a depth of the second trench structure is larger than a depth of the buried layer;
• performing a first ion implantation process to form a first doped region in the well at one side of the first trench structure, wherein the first doped region contacts the buried layer;
• performing a second ion implantation process to form a second well in the well at the other side of the first trench structure, wherein the second well has a second conductivity type and does not contact the buried layer;
• forming at least a gate on the semiconductor substrate, wherein the gate overlaps a part of the well between the first trench structure and the second trench structure;
• forming at least a third doped region in the first doped region;
• and
• forming at least a second doped region in the second well.