Abstract: A method for fabricating transistors such as high electron mobility transistors, each transistor comprising a plurality of epitaxial layers on a common substrate, method comprising: (a) forming a plurality of source contacts on a first surface of the plurality of epitaxial layers; (b) forming at least one drain contact on the first surface; (c) forming at least one gate contact on the first surface; (d) forming at least one insulating layer over and between the gate contacts, source contacts and the drain contacts; (e) forming a conductive layer over at least a part of the at least one insulating layer for connecting the source contacts; and (f) forming at least one heat sink layer over the conductive layer.