Patent ID: 8222108

Claim:
A method for manufacturing a trench MOSFET having source regions defined by a contact mask, comprising the steps of: growing an epitaxial layer with a first conductivity type upon a heavily doped substrate with said first conductivity type; applying a trench mask and forming a plurality of first gate trenches in source metal area, and at least a second gate trench having wider gate trench than said first gate trenches in gate runner metal area, and multiple third gate trenches in termination area; growing a sacrificial oxide layer onto inner surface of all the gate trenches to remove plasma damage; removing said sacrificial oxide layer and growing or depositing a first insulation layer along said inner surface of said first, second and third gate trenches as a gate oxide; forming doped polysilicon with said first conductivity type into said first, second and third gate trenches and etching back or CMP said doped polysilicon; implanting said epitaxial layer with a second conductivity type dopant and diffusing it to form body regions without having a body mask; depositing a second insulating layer functioning as a thick oxide interlayer on the top surface of the epitaxial layer and said first, second and third gate trenches; applying said contact mask and performing dry oxide etching to remove said oxide interlayer from contact open areas defined by said contact mask; implanting said contact open areas with source dopant without having a source mask, and further diffusing it to form said source regions with said first conductivity type; forming trenched source-body contacts into said body regions and at least a trenched gate contact into said doped polysilicon in said second gate trench by dry silicon and polysilicon etches through said contact open areas, respectively and simultaneously; and ion implanting said trenched source-body contacts with a dopant having said second conductivity type and activating it by RTA to form a body contact resistance reduction area with said second conductivity type around each of said trenched source-body contacts.