Trench transistor with self-aligned source

A method of forming a trench transistor, the method comprising:

• a) forming a trench in a substrate, the substrate having a surface and the trench having a first sidewall and a second sidewall;
• b) forming a gate structure in the trench;
• c) implanting a first dose of dopants such that a portion of the first dose is implanted through the first sidewall, and a further portion of the first dose is implanted through the surface;
• d) changing an orientation of the substrate by a predetermined number of degrees about an axis of implantation;
• and
• e) implanting a second dose of dopants such that a portion of the second dose is implanted through the second sidewall, and a further portion of the second dose is implanted through the surface,
• wherein a substantially L-shaped n+ source is formed.

A method of forming a trench transistor, the method comprising:

• growing an epitaxial layer on a semiconductor substrate;
• growing a field oxide on the epitaxial layer;
• forming at least one trench in the epitaxial layer, the at least one trench having;
• a first sidewall,
• a second sidewall, and
• a bottom surface;
• forming a gate dielectric layer inside the at least one trench;
• depositing a gate material in the at least one trench;
• etching the gate material to form a recess in the at least one trench;
• implanting well-forming dopants into the epitaxial layer adjacent to the at least one trench;
• driving-in the well-forming dopants to form a well region;
• forming a heavy body region inside the well region;
• forming a source mask;
• angle implanting the first sidewall of the at least one trench and the surface of the epitaxial layer;
• changing an orientation of the semiconductor substrate about an axis of implantation;
• angle implanting the second sidewall of the at least one trench and the surface of the epitaxial layer;
• and
• performing a thermal treatment.