Graphene is a promising material in next-generation devices. Large-scale epitaxial graphene should be grown on Si substrates to transfer the accumulated technologies to integrated devices. We have for this reason developed epitaxy of graphene on Si (GOS) and device operation of the backgate field-effect transistors (FETs) using GOS has been confirmed. It is demonstrated in this paper that the GOS method enables us to tune the structural and electronic properties of graphene in terms of the crystallographic orientation of the Si substrate. Furthermore, it is shown that the uniformity of the GOS process within a sizable area enables us to reliably fabricate topgate FETs using conventional lithography techniques. GOS can be thus the key material in next-generation devices owing to the tunability of the electronic structure by the crystallographic orientation of the Si substrate.