The　essential　step　for　epitaxial　growth　of　tetragonal　Mn3Ge　films　with　high　perpendicular　magnetic　anisotropy　(PMA)　is　to　choose　suitable　substrates　with　small　lattice　misfit.　The　exploration　process　has　involved　large　efforts　on　depositing　films　on　single　crystalline　substrates　using　buffer　layers　preferably　formed　from　Cr　or　Pt,　but　they　lacked　a　systematically　comparative　investigation　for　practical　applications.　This　study　investigates　the　structural,　surface　and　magnetic　properties　of　ultrathin　Fe　(2　nm)　seed　layer　to　induce　homoepitaxial　Mn3Ge　films　on　MgO　(0　0　1)　substrates　compared　with　that　of　the　heteroepitaxial　Mn3Ge　films　on　three　typical　buffer　layers,　such　as　Cr　(40　nm),　Cr　(20　nm)/Pt　(10　nm),　Fe　(2　nm)/Pt　(20　nm).　Furthermore,　a　correlation　between　film　strain　and　film　quality　has　been　established,　which　is　critical　for　spintronics　applications.　More　importantly,　we　attribute　the　homoepitaxial　growth　of　Mn3Ge　films　on　the　ultrathin　Fe　seed　layers　to　the　Fe　diffusion　and　formation　of　Fe-Mn-Ge　alloy　at　the　interface,　and　confirm　this　supposition　with　HAADF-STEM　characterizations.　The　Fe-doped　Mn3Ge　interlayer　can　act　as　the　gradual　buffer　layer,　and　lead　to　a　high-quality　crystal　structure　and　extremely　high　magnetic　squareness　ratio　of　Mn3Ge　films　in　a　large　range　of　thickness　(100　~　400　nm).　This　result　offers　a　new　concept　of　high-quality　growth　of　D022-Mn3Ge　films,　which　may　enhance　the　prospect　for　tetragonal　Mn3Ge　thin　films　in　superior　spintronics　applications.　©　2020　Elsevier　B.V.