NONVOLATILE SEMICONDUCTOR MEMORY DEVICE

摘要

PURPOSE:To completely enhance a reading margin without depending on a power source potential by comparing with a predetermined comparison potential to detect the data of a double gate type ROM element. CONSTITUTION:A floating gate of a transistor Mc of a potential generating circuit 30 of a comparison potential generating circuit 20 is brought to a neutral state. A potential variation owing to a variation of a power source voltage Vc of a nodal point Bc is equivalent to a cbange of a potential VBa1 owing to the variation of a voltage VCC of a nodal point Ba when ROM cells M11-Mmn of a double gate transistor in which the floating gate is brought to the neutral state. Similarly, the potential of a nodal point Bd of a comparison potential generating circuit 40 is equivalent to the variation of a potential VBa2 of the nodal point Ba when the cells M11-Mmn in which an electric charge flows in the floating gate. These nodal points Bc and Bd are connected by the transistor of a resistance component. A potential of a comparison voltage output nodal point D to a sense amplifier SA goes to an intermediate value of the potentials VBa1, VBa2. The reading margin of the ROM becomes high without depending on the power source potential.