Abstract: Unique EPROM and EEPROM devices are provided with a composite dielectric layer between the control gate and the floating gate which is sufficiently thick to provide electrical and physical integrity but also has a high equivalent dielectric constant. The use of the composite dielectric layer alleviates certain problems experienced in the prior art EPROM and EEPROM devices which utilize a polycrystalline silicon floating gate and a polycrystalline silicon control gate separated by an SiO.sub.2 dielectric layer, such as the problems of sharp silicon points resulting from polysilicon grain growth causing low dielectric breakdown strength. In contrast to the prior art, a composite dielectric layer serves as a partially relaxable dielectric between the control gate and the floating gate of an EEPROM or an EPROM. The composite dielectric layer provides high capacitance between the floating gate and the control gate without the insulative and breakdown problems encountered with prior art thin dielectric layers.