Metal/semiconductor　heterojunctions　have　attracted　interest　for　many　years　due　to　their　importance　in　electronic　device　applications.　Usually,　owing　to　a　large　lattice　mismatch　between　semiconductors　and　most　metals,　it　is　difficult　to　obtain　a　high-quality　epitaxial　interface　by　direct　deposition　of　metals　on　semiconductors.　In　this　work,　we　address　this　problem　by　proposing　a　novel　strategy　to　use　metal　oxides　as　templates.　Due　to　the　small　lattice　mismatch　between　CoO　and　GaN,　it　was　found　that　epitaxial　CoO　films　can　be　readily　formed　on　GaN.　Subsequent　decomposition　of　CoO　at　high　temperature　and　low　oxygen　pressure　gives　rise　to　an　epitaxial　metal　Co　film　on　GaN,　forming　a　Co/GaN　interface　of　good　quality,　and　the　inheritance　of　the　orientation　relationship　between　CoO　and　GaN,　i.e.,　(111)Co//(0001)GaN　and　[112¯]Co//[11¯00]GaN.　Additionally,　the　atomic　structures　and　electronic　properties　of　the　Co(111)/GaN(0001)　interface　are　investigated　by　combining　aberration-corrected　scanning　transmission　electron　microscopy　and　first-principles　calculations.　Utilizing　Co/GaN　as　a　model　system,　this　study　advances　insights　into　the　preparation　of　high-quality　epitaxial　metal/semiconductor　heterojunctions.　©　2023　The　Royal　Society　of　Chemistry.