SEMICONDUCTOR DEVICE AND MANUFACTURING METHOD THEREOF

摘要

PURPOSE: A semiconductor device and a manufacturing method thereof are provided to enable high-speed operation by improving the properties of a transistor. CONSTITUTION: A second oxide semiconductor layer is formed on a first oxide semiconductor layer. The electron affinity of the second oxide semiconductor layer is larger than the electron affinity of the first oxide semiconductor layer. The energy gap of the second oxide semiconductor layer is smaller than the energy gap of the first oxide semiconductor layer. A third oxide semiconductor layer covers the side and top surfaces of the second oxide semiconductor layer. A source electrode layer(405a) and a drain electrode layer(405b) are formed on the third oxide semiconductor layer. A gate insulating film(402) is formed on the source and drain electrode layers. [Reference numerals] (AA) Gate