A cutter element having a composite substrate

A method of forming a cutting element that includes filling at least one non-planar region on an upper surface 31 of a carbide substrate 33 with a diamond mixture 35, subjecting the substrate and the diamond mixture to high pressure high temperature sintering conditions to form a reduced coefficient of thermal expansion (CTE) substrate having polycrystalline diamond that extends a depth into the reduced-CTE substrate in an interface region 34, and an upper surface 32 made of a composite surface of diamond and carbide, and attaching a polycrystalline diamond body 38 to the composite surface of the reduced-CTE substrate is disclosed. Also independently claimed is providing carbide and diamond particles which are sintered to form a reduced-CTE substrate to which a polycrystalline diamond body is attached, and a cutting element comprising a polycrystalline diamond layer attached to a reduced-CTE substrate comprising diamond particles disposed in a matrix.