Patent ID: 8188573

Claim:
A nitride semiconductor substrate, comprising: an epitaxy substrate; a plurality of nitride pillars formed on the epitaxy substrate to expose surfaces of the epitaxy substrate that are between the nitride pillars and to expose side and bottom surfaces of the epitaxial substrate, wherein the plurality of nitride pillars comprises: a plurality of first patterned arranged pillars, wherein each of the plurality of the first patterned arranged pillars viewed from a cross section is a rectangle; and a plurality of second patterned arranged pillars formed on top of the first patterned arranged pillars, wherein a width of a cross-section of each of the second patterned arranged pillars is smaller than a width of a cross-section of each of the first patterned arranged pillars, and a distance among each of the second patterned arranged pillars is longer than a distance among each of the first patterned arranged pillars, wherein each of the plurality of the second patterned arranged pillars viewed from the cross section is a rectangle; a nitride semiconductor layer formed on top of the plurality of nitride pillars; and a mask layer covering all the exposed surfaces of the epitaxy substrate that are between the nitride pillars and covering vertical surfaces of the first patterned arranged pillars and vertical surfaces of the second patterned arranged pillars.