Production method for high-purity lanthanum, high-purity lanthanum, sputtering target composed of

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A production method for high-purity lanthanum having a purity of 4N or more excluding rare earth elements other than lanthanum and gas components, the method being characterized by the production of lanthanum having a purity of 4N or more by reducing, with distilled calcium, a lanthanum fluoride starting material that has a purity of 4N or more excluding rare earth elements other than lanthanum and gas components, and the removal of volatile substances by electron beam melting. The production method for high-purity lanthanum is characterized in that Al, Fe, and Cu are each contained in an amount of 10 wtppm or less. The production method for high-purity lanthanum is also characterized in that the total amount of gas components is 1000 wtppm or less. In this manner the present invention addresses the problem of providing a technique capable of efficiently and stably providing high-purity lanthanum, a sputtering target composed of high-purity lanthanum, and a thin film for metal gate that contains high-purity lanthanum as a main component.