Oxide semiconductor, semiconductor device, semiconductor memory device, and solid-state imaging device

Embodiments of the invention relate to an oxide semiconductor, a semiconductor device, a semiconductor memory device, and a solid-state imaging device. Provided are an oxide semiconductor with improved heat resistance, a semiconductor device, a semiconductor memory device, and a solid-state imaging device. According to one embodiment, an oxide semiconductor includes indium (In), gallium (Ga), andsilicon (Si). A composition ratio of Si to In (Si/In) in the oxide semiconductor is larger than 0.2, and a composition ratio of Si to Ga (Si/Ga) in the oxide semiconductor is larger than 0.2. 本发明的实施方式涉及氧化物半导体、半导体装置、半导体存储装置及固体摄像装置。提供种提高了耐热性的氧化物半导体、半导体装置、半导体存储装置及固体摄像装置。根据实施方式，提供种含有铟(In)、镓(Ga)和硅(Si)的氧化物半导体。所述氧化物半导体中的Si与In的组成比(Si/In)大于0.2。所述氧化物半导体中的Si与Ga的组成比(Si/Ga)大于0.2。