Patent ID: 8728878
Filing Date: 2014-05-20
Classification: H01L

Abstract:
1. A method for fabricating a metal-oxide-semiconductor (MOS) P-N junction diode device, comprising steps of: providing a substrate having a first conductivity type, wherein the first conductivity type is a n type; forming a first mask layer having an opening on the substrate; doping the substrate with ions having a second conductivity type through the opening to form a guard ring in the substrate, wherein the second conductivity type is a p type; partially removing the first mask layer to form a field oxide structure defining a trench structure; sequentially forming a gate structure, a second mask layer and a first patterned photo-resist layer defining the gate structure in the trench structure; performing an isotropic etching step on the second mask layer by using the first patterned photo-resist layer as a mask to have the remaining second mask layer shorter than the first patterned photo-resist layer; doping the substrate with ions having the second conductivity type using the first patterned photo-resist layer as a mask to form a first p type Boron ion doped sub-region in the substrate; removing the first patterned photo-resist layer; doping the substrate with ions having the second conductivity type by using the remaining second mask layer as a mask to form a second p type Boron ion doped sub-region in the substrate, wherein the first p type Boron ion doped sub-region and the second p type Boron ion doped sub-region define a single p type Boron ion doped region; removing the remaining second mask layer; and forming a top electrode contacted to the single p type Boron ion doped region, the trench structure and the field oxide structure, and forming a bottom electrode on a surface of the substrate opposite to the top electrode; wherein the guard ring in the substrate is adjacent to the field oxide structure and the single p type Boron ion doped region, the first p type Boron ion doped sub-region is shallower than the p type guard ring, the second p type Boron ion doped sub-region is shallower than the first p type Boron ion doped sub-region, and the second p type Boron ion doped sub-region is disposed between the gate structure and the first p type Boron ion doped sub-region.