The present invention refers to a furnace apparatus (100), in particular a furnace apparatus (100) for growing crystals, in particular for growing SiC crystals. The furnace apparatus comprises a furnace unit (102), wherein the furnace unit (102) comprises a furnace housing (108) at least one crucible unit (106) wherein the crucible unit (106) is arranged inside the furnace housing (108), wherein the crucible unit (106) comprises a crucible housing (110), wherein the housing (110) has an outer surface (112) and an inner surface (114), wherein the inner surface (114) at least partially defines a crucible volume (116), wherein a receiving space (118) for receiving a source material (120) is arranged or formed inside the crucible volume (116), wherein a seed holder unit (122) for holding a defined seed wafer (18) is arranged inside the crucible volume (116), and at least one heating unit (124) for heating the source material (120), wherein the receiving space (118) for receiving the source material (120) is at least in parts arranged between the heating unit (124) and the seed holder unit (122).