Process method and structure for high voltage MOSFETS

A method for manufacturing a semiconductor power device on a semiconductor substrate comprising:

• depositing a hard mask atop the semiconductor substrate and patterning the hard mask according to a pre-determined trench configuration;
• etching the semiconductor substrate through the patterned hard mask to form a plurality of trenches in the semiconductor substrate along a longitudinal direction having trench sidewalls along the longitudinal direction and forming in at least one of the trenches a laterally notch to form a laterally notch trench sidewall that extends laterally along a nonlinear direction relative to the longitudinal direction thus exposing an entire vertical length of the laterally notch trench sidewall facing the longitudinal direction;
• applying a vertical high energy implant to form trench bottom dopant regions below a trench bottom surface and also forming upper partial sidewall dopant region disposed on an upper portion of the trench sidewalls along the longitudinal direction followed by removing the hard mask;
• depositing an insulation layer for covering trench sidewalls and an insulation layer for covering the trench bottom surfaces;
• and
• applying a low energy tilt implant along the longitudinal direction of the trenches to implant to the laterally notch trench sidewall to form a sidewall dopant region along the entire vertical length of the laterally notch trench sidewall while maintaining the upper partial dopant region disposed on the upper portion of the trenches sidewalls along the longitudinal direction at a distance above the trench bottom surfaces.