Abstract: A semiconductor device has a substrate of one type of semiconductor material, such as silicon. A contact structure is formed on the substrate, and the contact structure is formed of a compound of a metal and a second type of semiconductor material, such as germanium. The contact structure according to embodiments of the present invention include a semiconductor material which a different semiconductor material forming the substrate. Higher or lower barrier height is obtained by embodiment of the invention. A method for forming a contact structure in which a substrate of one type of semiconductor material is provided. A layer of another different semiconductor material is formed on the substrate. A layer of metal is then formed on the layer of the other different semiconductor material. Upon annealing, a contact structure is formed on the substrate, which is a compound of the metal and the other different semiconductor material, onto the substrate.

Abstract: There is provided a quantum-key distribution method between a plurality of users or groups. A center prepares a predetermined number of entangled states consisting of qubits equal to the number of the users, and generates quantum states consisting of the qubits belonging to each of the entangled states and corresponding to each of the users. The center transmits each of the quantum states to each of the users after an authentication process. Each of the users receiving the quantum state makes public an axis used to measure each of the qubits constituting the quantum states. The number of users in each group measuring the qubits with a predetermined axis is represented by module 4. If the sum of the module 4 of each group is even, each group collects the qubit measurement results of the users and acquires each group key. Therefore, it is possible to provide a high-security quantum-key distribution method between an unspecified number of users or groups.