Manufacturing method of semiconductor device

Abstract

A semiconductor layer containing a metal oxide is formed, a gate insulating layer containing an oxide is formed over the semiconductor layer, and a metal oxide layer is formed over the gate insulating layer. Heat treatment is performed after the metal oxide layer is formed, and the metal oxide layer is removed after the heat treatment is performed. After the metal oxide layer is removed, a gate electrode overlapping with part of the semiconductor layer is formed over the gate insulating layer. Then, a first element is supplied through the gate insulating layer to a region of the semiconductor layer that does not overlap with the gate electrode. Examples of the first element include phosphorus, boron, magnesium, aluminum, and silicon. The steps performed after the metal oxide layer is removed are each preferably performed at a temperature lower than or equal to the temperature of the heat treatment.

Dependencies are inferred from the claim text.