MOSFET with isolation structure and fabrication method thereof

A P-type MOSFET, comprising:

• a P-type substrate;
• a second N-type buried layer and a P-type epitaxial layer, formed in the P-type substrate;
• a second N-type diffusion region having N conductivity-type ions, forming a second N-well in the second N-type buried layer;
• a second P-type diffusion region having P conductivity-type ions, forming a second P-type region in the second N-well;
• a second drain diffusion region having P+ conductivity-type ions, forming a second drain region in the second P-type diffusion region;
• a second source diffusion region having P+ conductivity-type ions, forming a second source region, wherein a second channel is formed between the second source region and the second drain region;
• a second contact diffusion region having N+ conductivity-type ions, forming a second contact region, wherein the second N-type diffusion region surrounds the second source region and the second contact region;
• a plurality of separated P-type diffusion regions having P conductivity-type ions, forming a plurality of separated P-type regions in the P-type epitaxial layer, so as to provide an isolation effect;
• a second thin gate oxide layer and a second thick field oxide layer, formed on the P-type substrate;
• a second gate, disposed on the second thin gate oxide layer and the second thick field oxide layer, for controlling an amount of current in the second channel;
• a silicon oxide insulating layer, covering the second gate and the second thick field oxide layer;
• a second drain metal contact, having a third metal electrode connected with the second drain diffusion region;
• a second source metal contact, having a fourth metal electrode connected to the second contact diffusion region and the second source diffusion region;
• and
• a second gap, formed between the second thick field oxide layer and the second N-well, for raising a breakdown voltage of the P-type MOSFET.

A method of fabricating an N-type MOSFET, comprising:

• forming a P-type substrate;
• forming a first N-type buried layer and a P-type epitaxial layer in the P-type substrate;
• forming a first N-well in the first N-type buried layer in a first N-type diffusion region having N conductivity-type ions;
• forming a first P-type region in the first N-well in a first P-type diffusion region having P conductivity-type ions;
• forming a first drain region in the first N-type diffusion region in a first drain diffusion region having N+ conductivity-type ions;
• forming a first source region in a first source diffusion region having N+ conductivity-type ions, wherein a first channel is formed between the first source region and the first drain region;
• forming a first contact region in a first contact diffusion region having P+ conductivity-type ions, wherein the first P-type diffusion region surrounds the first source region and the first contact region;
• forming a plurality of separated P-type regions in the P-type epitaxial layer in a plurality of separated P-type diffusion regions having P conductivity-type ions, so as to provide an isolation effect;
• forming a first thin gate oxide layer and a first thick field oxide layer on the P-type substrate;
• disposing a first gate on the first thin gate oxide layer and the first thick field oxide layer, for controlling an amount of current in the first channel;
• covering the first gate and the first thick field oxide layer with a silicon oxide insulating layer;
• forming a first drain metal contact having a first metal electrode connected with the first drain diffusion region;
• forming a first source metal contact having a second metal electrode connected to the first source diffusion region and the first contact diffusion region;
• and
• forming a first gap between the first thick field oxide layer and the first P-type region, for raising a breakdown voltage of the N-type MOSFET.

A method of fabricating a P-type MOSFET, comprising:

• forming a P-type substrate;
• forming a second N-type buried layer and a P-type epitaxial layer in the P-type substrate;
• forming a second N-well in the second N-type buried layer in a second N-type diffusion region having N conductivity-type ions;
• forming a second P-type region in the second N-well in a second P-type diffusion region having P conductivity-type ions;
• forming a second drain region in the second P-type diffusion region in a second drain diffusion region having P+ conductivity-type ions;
• forming a second source region in a second source diffusion region having P+conductivity-type ions, wherein a second channel is formed between the second source region and the second drain region;
• forming a second contact region in a second contact diffusion region having N+ conductivity-type ions, wherein the second N-type diffusion region surrounds the second source region and the second contact region;
• forming a plurality of separated P-type regions in the P-type epitaxial layer in a plurality of separated P-type diffusion regions having P conductivity-type ions, so as to provide an isolation effect;
• forming a second thin gate oxide layer and a second thick field oxide layer on the P-type substrate;
• disposing a second gate on the second thin gate oxide layer and the second thick field oxide layer, for controlling an amount of current in the second channel;
• covering the second gate and the second thick field oxide layer with a silicon oxide insulating layer;
• forming a second drain metal contact having a third metal electrode connected with the second drain diffusion region;
• forming a second source metal contact having a fourth metal electrode connected to the second contact diffusion region and the second source diffusion region;
• and
• forming a second gap between the second thick field oxide layer and the second N-well, for raising a breakdown voltage of the P-type MOSFET.