Semiconductor resurf devices formed by oblique trench implantation

A method of manufacturing a semiconductor device comprising the steps of:

• providing a semiconductor substrate having first and second main surfaces opposite to each other, said semiconductor substrate having a heavily doped region of a first conductivity type at said second main surface and having a lightly doped region of the first conductivity type at said first main surface side,
• providing in said semiconductor substrate a plurality of trenches having a first extending portion extending from said first main surface into said heavily doped region to a first depth position while having a sidewall surface with a predetermined inclination maintained relative to said first main surface,
• obliquely implanting a dopant of the first conductivity type in a mesa region of said semiconductor substrate between an adjacent pair of said plurality of trenches at a sidewall surface of one trench, to form at the sidewall surface of said one trench a first doped region of the first conductivity type having a doping concentration lower than that of said heavily doped region, and
• obliquely implanting a dopant of the second conductivity type in said mesa region at a sidewall surface opposite to the sidewall implanted with said dopant of the first conductivity type, to provide a second doped region of the second conductivity type at the sidewall surface opposite to the sidewall implanted with said dopant of the first conductivity type, to provide a p-n junction of the first and second doped regions located along the depth direction of said plurality of trenches,
• said first depth position being closer to said second main surface than a junction of said heavily and lightly doped regions to said second main surface by at least a diffusion length of each of said dopants of the first and second conductivity types in manufacturing the semiconductor device,
• said dopants of the first and second conductivity types being each implanted at an angle allowing each of said dopants of the first and second conductivity types to be directly introduced into a sidewall surface of said treches located at a depth closer to said second main surface than said junction of said heavily and lightly doped regions to said second main surface by at least said diffusion length of each of said dopants of the first and second conductivity types in manufacturing the semiconductor device.