Patent ID: 8592292

Claim:
A method comprising: forming a first epitaxial layer over a semiconductor substrate; etching the first epitaxial layer to form multiple separated first epitaxial regions; forming a second epitaxial layer over the etched first epitaxial layer, each of the epitaxial layers comprising at least one Group III-nitride, the epitaxial layers collectively forming a buffer; forming a device layer over the buffer; fabricating a semiconductor device using the device layer; prior to forming the second epitaxial layer, depositing a first dielectric material over and around the first epitaxial regions and planarizing the first dielectric material and the first epitaxial regions; etching the second epitaxial layer to form multiple separated second epitaxial regions; and depositing a second dielectric material over and around the second epitaxial regions and planarizing the second dielectric material and the second epitaxial regions.