Asymmetric transient voltage suppressor device and methods for formation

A transient voltage suppression (TVS) device assembly, comprising:

• a TVS device, the TVS device comprising:
• a substrate base formed in a substrate, the substrate base comprising a semiconductor of a first conductivity type;
• an epitaxial layer, comprising a first thickness, and disposed on the substrate base, on a first side of the substrate, the epitaxial layer further comprising:
• a first epitaxial portion, the first epitaxial portion comprising the first thickness, and being formed of a semiconductor of a second conductivity type;
• a second epitaxial portion, the second epitaxial portion comprising an upper region, the upper region formed of the second conductivity type, and having a second thickness less than the first thickness,
• wherein a buried diffusion region is disposed in a lower region of the epitaxial layer in the second epitaxial portion, the buried diffusion region being formed of a semiconductor of the first conductivity type;
• and
• a leadframe, the leadframe being coupled to the TVS device on the first side of the substrate.

A method, comprising:

• providing a substrate having a base layer of a first conductivity type;
• forming an epitaxial layer of a second conductivity type on the base layer, wherein the epitaxial layer is disposed on a first side of the substrate, and having a first thickness;
• forming a first epitaxial portion and a second epitaxial portion within the epitaxial layer, wherein the first epitaxial portion is electrically isolated from the second epitaxial portion;
• and
• forming a buried diffusion region in the second epitaxial portion, the buried diffusion region extending at least to an interface between the epitaxial layer and the substrate base, wherein the buried diffusion region comprises the first conductivity type, wherein the buried diffusion region defines an upper region of the second epitaxial portion, the upper region comprising the second conductivity type, and having a second thickness less than the first thickness.