Patent ID: 9543431
Date: 2017-01-10
CPC Classifications: H01L

Claim:
1. A radio frequency laterally diffused metal oxide transistor (LDMOS) device comprising: a heavily doped silicon substrate of a first conductivity type; a silicon epilayer of the first conductivity type formed on the surface of the silicon substrate; a body region composed of an injection region of ions of the first conductivity type formed on a selected region of the silicon epilayer; a drift region composed of a first injection region and a second injection region of a second conductivity type formed on another selected region of the silicon epilayer; a polysilicon gate formed on top of the body region, isolated from the silicon epilayer by a gate media layer, covering a part of the body region, and extending to be on top of the drift region, wherein a surface of the part of the body region covered by the polysilicon gate is employed to form a channel; a first Faraday shielding layer covering a step structure of a second side of the polysilicon gate, a first shielding media layer being isolated in-between the first Faraday shielding layer and the polysilicon gate or the silicon epilayer on a bottom of the first Faraday shielding layer; a second Faraday shielding layer covering a step structure of the first Faraday shielding layer, a second shielding media layer being isolated in-between the second Faraday shielding layer and the first Faraday shielding layer or the silicon epilayer on a bottom of the second Faraday shielding layer; a source region which is composed of a heavily doped region of the second conductivity type formed in the body region and which is self-aligned with a first side of the polysilicon gate; a drain region which is composed of a heavily doped region of the second conductivity type formed in the drift region and which is distanced with a transverse distance from the second side of the polysilicon gate; a deep contact hole which is composed of a metal filled within a deep trench sinker, wherein the deep trench sinker passing through the source region, the body region and the silicon epilayer and into the silicon substrate, and which electrically connects the source region, the body region, the silicon epilayer and the silicon substrate; and transversely, the first injection region is situated between the second lateral surface of the polysilicon gate and the second lateral surface of the first Faraday shielding layer, wherein the second lateral surface of the first Faraday shielding layer is a lateral surface of a side near the drain region; the second injection region is situated between the second lateral surface of the first Faraday shielding layer and the drain region and encircles the drain region; a second lateral surface of the second Faraday shielding layer is a surface of a side near the drain region, wherein a maximum electric field strength of the drift region on the bottom of the second Faraday shielding layer increases as a doping concentration on the bottom of the second Faraday shielding layer increases; a doping concentration of the first injection region is higher than that of the second injection region, and under a condition guaranteeing that an electric field intensity of the first injection region is smaller than the maximum electric field strength of the drift region, the electric field intensity of the first injection region, a breakdown voltage and a saturation current of the radio frequency LDMOS device all increase with the increase of the doping concentration of the first injection region.