Superjunction structures for power devices and methods of manufacture

A method of forming a power device having an active region surrounded by a termination region, the method comprising:

• forming a plurality of trenches in at least one epitaxial layer of a first conductivity type;
• and
• filling the plurality of trenches with silicon material of a second conductivity type, the silicon material of the second conductivity type, together with a plurality of mesas defined in the at least one epitaxial layer by the plurality of trenches, defining a plurality of concentric octagon-shaped pillars of alternating conductivity type, at least a first portion of the concentric octagon-shaped pillars being disposed in the active region and at least a second portion of the concentric octagon-shaped pillars being disposed in the termination region,
• each of the plurality of concentric octagon-shaped pillars having a first four legs of a first length and a second four legs of a second length, the second length being different than the first length, and
• sidewalls of trenches defining the first four legs and the second four legs of each of the plurality of concentric octagon-shaped pillars having a same crystallographic plane direction.

A power device comprising:

• an epitaxial layer of a first conductivity type;
• an active region disposed in the epitaxial layer of the first conductivity type;
• a termination region disposed in the epitaxial layer of the first conductivity type and surrounding the active region;
• a plurality of trenches disposed in the epitaxial layer of the first conductivity type;
• and
• an epitaxial layer of a second conductivity type disposed in the plurality of trenches, the epitaxial layer of the second conductivity type, together with a plurality of mesas defined in the epitaxial layer of the first conductivity type by the plurality of trenches, defining a plurality of concentric octagon-shaped pillars of alternating conductivity type, at least a first portion of the concentric octagon-shaped pillars being disposed in the active region and at least a second portion of the concentric octagon-shaped pillars being disposed in the termination region,
• each of the plurality of concentric octagon-shaped pillars having a first four legs of a first length and a second four legs of a second length, the second length being different length than the first length, and
• sidewalls of trenches defining the first four legs and the second four legs of each of the plurality of concentric octagon-shaped pillars having a (tan 22.5)10> crystallographic plane direction.