Radio frequency LDMOS device and a fabrication method therefor

A fabrication method for the radio frequency LDMOS device, the method comprising:

• Step 1. forming a silicon epilayer of a first conductivity type by means of epitaxial growth on a surface of a heavily doped silicon substrate of the first conductivity type;
• Step 2. forming respectively a first injection region and a second injection region on a selected region of the silicon epilayer by means of injecting ions of a second conductivity type, and composing the first injection region and the second injection region into a drift region;
• transversely, the first injection region is situated between a second lateral surface of a polysilicon gate subsequently formed and a second lateral surface of a first Faraday shielding layer, wherein the second lateral surface of the first Faraday shielding layer is a lateral surface of a side near a 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 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;
• Step 3. growing a gate media layer on a surface of the silicon epilayer;
• Step 4. depositing a polysilicon on a surface of the gate media layer;
• Step 5. etching the polysilicon by means of chemical wet etching to form a polysilicon gate as a grid electrode of the radio frequency LDMOS device;
• a second side of the polysilicon gate extending to be on top of the drift region;
• Step 6. injecting ions of the first conductivity type in a selected region of the silicon epilayer to form a body region, the selected region for forming the body region being defined according to etching technique and being self-aligned with the polysilicon gate, a surface of the body region covered by the polysilicon gate being employed to form a channel;
• Step 7. injecting heavily doped ions of the second conductivity type to form a source region and a drain region, the source region being self-aligned with a first side of the polysilicon gate;
• the drain region being distanced with a transverse distance from a second side of the polysilicon gate and being located in the drift region;
• Step 8. successively forming a first shielding media layer and the first Faraday shielding layer, the first Faraday shielding layer covering on a step structure of the second side of the polysilicon gate and being isolate on a bottom thereof with the first shielding media layer from the polysilicon gate or the epilayer;
• Step 9. successively forming a second shielding media layer and the second Faraday shielding layer, the second Faraday shielding layer covering on a step structure of the first Faraday shielding layer and being isolate on a bottom thereof with the second shielding media layer from the first Faraday shielding layer or the epilayer;
• and
• Step 10. etching a deep trench sinker which passes though the source region, the body region, and the epilayer and enters the silicon substrate;
• filling the deep trench sinker with a metal to form a deep contact hole which electrically connects the source region, the body region, the epilayer and the silicon substrate.