This　Letter　demonstrates　a　beta-phase　gallium　oxide　(beta-Ga2O3)　vertical　Schottky　barrier　diode　(SBD)　with　mesa　termination　assisted　by　a　partially　suspended　field　plate,　which　is　fabricated　on　the　epitaxial　thick　film　grown　by　metal-organic　chemical　vapor　deposition.　The　epitaxial　film　features　a　high-quality,　smooth　surface　and　high　mobility,　laying　the　foundation　for　achieving　high　performances.　In　the　device　aspect,　the　mesa　termination　and　the　partially　suspended　field　plate,　which　can　be　formed　simultaneously　by　adding　Cl-2　during　the　inductively　coupled　plasma　etching　process　to　facilitate　isotropic　etching　of　beta-Ga2O3,　effectively　mitigate　the　electric　field　crowding　phenomenon　at　the　device　edge,　thereby　reducing　the　electric　field　peaks　both　in　the　epitaxial　layer　and　dielectric　layer　and　improving　the　breakdown　voltage　(BV).　The　experimental　results　show　that　the　proposed　SBD　achieves　a　high　BV　of　3.45　kV　and　a　low　specific　on　resistance　of　3.88　m　Omega　cm(2),　yielding　a　high　power　figure　of　merit　of　3.07　GW/cm(2).　Meanwhile,　a　low　forward　voltage　(at　100　A/cm(2))　of　1.25　V　can　also　be　obtained,　verifying　the　low　conduction　loss　property.