The present technology relates to a semiconductor device providing an image sensor package capable of coping with an increase in the number of I/Os of an image sensor, a manufacturing method thereof, and an electronic apparatus. The semiconductor device includes an image sensor, a glass substrate, a wiring layer, and external terminals. In the image sensor, photoelectric conversion elements are formed on a semiconductor substrate. The glass substrate is arranged on a first main surface side of the image sensor. The wiring layer is formed on a second main surface side opposite to the first main surface. Each of the external terminals outputs a signal of the image sensor. Metal wiring of the wiring layer extends to an outer peripheral portion of the image sensor and is connected to the external terminals. The present technology can be applied to, for example, an image sensor package and the like.