NOVELTY - A solid state device comprises a structure having region (R1) having single crystal of primary crystallographic orientation and a composition (C1), a region (R2) having single crystal of secondary crystallographic orientation and a composition (C2), and a region (R3) having single crystal of another crystallographic orientation (a) and composition (C3). The region (R3) is separated from region (R1) by the region (R2). The region (R2) contains rare earth metal compound(s) such that the crystallographic orientation (a) is different from primary crystallographic orientation.    USE - Solid state device e.g. field effect transistor, multiple gate field effect transistor, vertical gate field effect transistor, electronic memory, magnetic sensor and storage, semiconductor optical amplifier, semiconductor photo-detector, semiconductor laser, bipolar transistor, CMOS device, light emitting device, solar cell, photo-voltaic device and thermoelectric device (claimed).    ADVANTAGE - The solid state device has improved carrier mobility.    DETAILED DESCRIPTION - A solid state device comprises a structure having region (R1) having single crystal of primary crystallographic orientation and a composition (C1), a region (R2) having single crystal of secondary crystallographic orientation and a composition (C2), and a region (R3) having single crystal of another crystallographic orientation (a) and composition (C3). The region (R3) is separated from region (R1) by the region (R2). The region (R2) contains rare earth metal compound(s) such that the crystallographic orientation (a) is different from primary crystallographic orientation. The composition (C1,C3) contain IV group element(s). The composition (C1) contains gallium arsenide, indium phosphide, indium arsenide, cadmium telluride, zinc telluride, indium-gallium-arsenide-nitride and/or indium antimonide, or aluminum oxide. The composition (C2) contains lanthanide series plus yttrium, carbon, silicon, germanium, oxygen, nitrogen and phosphorus. The composition (C3) contains binary and ternary alloy of silicon-germanium-carbon and rare earth carbide.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of metal oxide semiconductor field effect transistor device.