High Voltage LDMOS Device with an Increased Voltage at Source (High Side) and a Fabricating Method Thereof

A fabricating method for the high voltage LDMOS device with the high side source voltage, the method comprising:

• Step 1:
• injecting ions into a p type substrate to form an n type injection region;
• Step 2:
• injecting ions into the p type substrate to form a p type injection region;
• a lateral surface of the p type injection region and a lateral surface of the n type injection region being not in contact with one another, and being distant with one another with a distance;
• Step 3:
• forming an n type epitaxial layer on top of the p type substrate;
• transforming the p type injection region to a p type buried layer, and the n type injection region to an n type buried layer;
• the p type buried layer and the n type buried layer being both situated on an interface between the p type substrate and the n type epitaxial layer;
• Step 4:
• growing a first silicon oxide via thermal oxidation on a surface of the n type epitaxial layer, depositing a silicon nitride, and removing portions of the silicon nitride and the first silicon oxide via photoetching;
• subsequently growing a second silicon oxide via thermal oxidation on an exposed surface of the n type epitaxial layer to be an isolating structure;
• and finally removing the silicon nitride via wet etching;
• Step 5:
• forming an n well via injecting ions into the n type epitaxial layer;
• Step 6:
• forming an n type drift region on top of the n well;
• Step 7:
• forming a first p well and a second p well in the n type epitaxial layer;
• wherein the first p well, the p type buried layer and the n type buried layer constituting an isolating ring surrounding the LDMOS;
• Step 8:
• growing a third silicon oxide via thermal oxidation on the n type epitaxial layer, depositing a polysilicon, and subsequently forming a polysilicon gate and a gate oxide layer thereunder;
• Step 9:
• injecting ions for forming a substrate terminal in the first p well, for forming a drain in the drift region, and for forming a source and a body terminal in the second p well;
• wherein the drain and the p type buried layer overlaps at least partially in the vertical direction, and the source and the body terminal are centrally on top of the n type buried layer.