Oki Electric Industry Co., Ltd.

Shoji Kitazawa

Takashi Ono

Teruhiro Harada

Yoshimasa Sekino

A nonvolatile semiconductor memory device includes a plurality of memory cells. A couple of bits of data can be stored in the memory cell, the stored data being controlled according to resistance values of first and second variable resistance regions. One of the plurality of memory cells shares its first diffusion layer with an adjacent memory cell and shares its second diffusion layer with another adjacent memory cell. The first diffusion layers of the plurality of memory cells are coupled to each other with a first conductive line extending in a first direction. The second diffusion layers of the plurality of memory cells are coupled to each other with a second conductive line extending in the first direction. The gate electrodes of the plurality of memory cells are coupled to each other with a third conductive line extending in a second direction, which is orthogonal to the first direction.

Nonvolatile semiconductor memory device

A power-on reset circuit is capable of outputting a normal reset signal despite slow rise of power supply voltage. A node is interposed between a MOS capacitor including a PMOS with its drain and source connected in common and an NMOS having its gate fixedly connected to a ground potential. The node is connected to a ground potential via the NMOS and also to a power supply line via the MOS capacitor. Therefore, even when the power supply voltage rises slowly after power is turned on, the potential of the node rises substantially at the same rate as the power supply voltage. After the power supply voltage reaches a predetermined power supply potential, the potential of the node is gradually lowered due to an off leakage current through the NMOS. The node is connected with an inverter operating according to the power supply voltage. When the potential of the node decreases below &#xbd; of the power supply voltage, the reset signal outputted from the inverter goes to the H level.

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Tokyo, Japan

Shoji Kitazawa