HIGH-PURITY ERBIUM, SPUTTERING TARGET COMPRISING HIGH-PURITY ERBIUM, METAL GATE FILM HAVING HIGH-P

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High-purity erbium having : a purity of at least 5N, excluding rare-earth elements and gas components; no more than 1 wt ppm each of Al, Fe, Cu, and Ta; no more than 10 wt ppm of W; no more than 150 wt ppm of carbon; no more than 1 wt ppm each of alkali metals and alkali rare earth metals; no more than 10 wt ppm in total of other transition metal elements; and no more than 10 wt ppb each of the radioactive elements U and Th. The present invention addresses the problem of providing : a method for increasing the purity of erbium, which has a high vapor pressure and is difficult to purify in a molten state; high-purity erbium obtained by said method; and technology capable of efficiently and stably providing a sputtering target comprising high-purity material erbium and a metal gate thin film having the high-purity erbium as the main component.