A method of fabricating a GaN HEMT includes growing a first epitaxial layer on a substrate, growing a second epitaxial layer on the first epitaxial layer, growing a third epitaxial layer on the second epitaxial layer, depositing a first dielectric film on the third epitaxial layer, using dielectric films to form a first sidewall dielectric spacer, forming a sidewall gate adjacent the first sidewall dielectric spacer. The sidewall gate may be made to be less than 50 nm in length.