High voltage power MOSFET having a voltage sustaining region that includes doped columns formed by trench etching and diffusion from regions of oppositely doped polysilicon

A power semiconductor device comprising:

• a substrate of a first or second conductivity type;
• a voltage sustaining region disposed on said substrate, said voltage sustaining region including:
• an epitaxial layer having a first conductivity type;
• at least one trench located in said epitaxial layer;
• a first layer of material located in the trench;
• a second layer of material located over the first layer of polysilicon;
• at least one doped column located adjacent to the trench and in the epitaxial layer, said at least one doped column having a dopant of the second conductivity type, said at least one doped column being formed by diffusion of the second dopant from the first layer of material into the epitaxial layer;
• at least one region of said second conductivity disposed over said voltage sustaining region to define a junction therebetween.

A method of forming a power semiconductor device comprising the steps of:

• A. providing a substrate of a first or second conductivity type;
• B. forming a voltage sustaining region on said substrate by:
• 1. depositing an epitaxial layer on the substrate, said epitaxial layer having a first conductivity type;
• 2. forming at least one trench in said epitaxial layer;
• 3. providing in said trench a first layer of material having a second dopant of the second conductivity type;
• 4. diffusing said second dopant to form a doped epitaxial region adjacent to said trench and in said epitaxial layer;
• 5. providing in said trench a second layer of material having a first dopant of the first conductivity type;
• 6. interdiffusing the first and second dopants respectively located in the second and first layers of material to achieve electrical compensation in the first and second layers of material;
• C. forming over said voltage sustaining region at least one region of said second conductivity type to define a junction therebetween.

A method of forming a power semiconductor device comprising the steps of:

• A. providing a substrate of a first or second conductivity type;
• B. forming a voltage sustaining region on said substrate by:
• 1. depositing an epitaxial layer on the substrate, said epitaxial layer having a first conductivity type;
• 2. forming at least one trench in said epitaxial layer;
• 3. providing in said trench a first layer of material having a second dopant of the second conductivity type;
• 4. diffusing said second dopant to form a doped epitaxial region adjacent to said trench and in said epitaxial layer;
• 5. diffusing a first dopant of the first conductivity type into the first layer of material to achieve electrical compensation in the first layer of material;
• C. forming over said voltage sustaining region at least one region of said second conductivity type to define a junction therebetween.