▎ 摘　　要

NOVELTY - The substrate (1) has a graphene layer (13) that is formed by laminating several graphene layers. A silicon carbide layer (14) is formed on the surface of the graphene layer. The graphene layer is arranged between silicon carbide layer and a support substrate (11). The silicon carbide layer is located between graphene layer and main portion. A channel layer is formed on the main portion. Several graphenes are stacked on the channel layer. A dope layer is formed in surface of channel layer. USE - Silicon carbide single crystal substrate for semiconductor element such as high electron mobility transistor (HEMT) and MOSFET for use in communication apparatus and semiconductor laser apparatus. ADVANTAGE - The operating efficiency of communication apparatus can be improved effectively, since graphene layer is arranged between silicon carbide layer and support substrate. The switching speed of a semiconductor element can be improved. The quality of silicon carbide single crystal substrate can be improved. DETAILED DESCRIPTION - The substrate has source, gate and drain electrodes that are formed in surface of the dope layer. The dope layer is made up of silicon carbide polycrystal. A buffer layer is arranged between channel layer and main portion. A protective layer is formed between source and drain electrodes, to cover surface of the dope layer. An INDEPENDENT CLAIM is included for manufacturing method of semiconductor element, involves introducing reactive gas and hydrogen carrier gas on the main portion. The temperature of reactive gas and hydrogen carrier gas is maintained at the specific range. DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the silicon carbide single crystal substrate. Silicon carbide single crystal substrate (1) Support substrate (11) Silicon carbide layer (12,14) Graphene layer (13)