Abstract: An EPROM device erasable with ultraviolet rays is made with a container of plastic material opaque to ultraviolet rays having a window overlying the semiconductor chip. Plastic material transparent to ultraviolet rays fills the interior space of the container over said chip. The container is formed by moulding of the mass of transparent plastic material previously formed on the semiconductor chip, or a container formed preliminarily is filled with a semiconductor chip and then with a mass of transparent plastic material and finally closed with a transparent lens which fixes the thickness of the transparent mass, distributing it uniformly in the interior space of the container.