A 4-Mbit dynamic RAM has been designed and fabricated using 1.0-μm twin-tub CMOS technology. The memory array consists of trenched n-channel depletion-type capacitor cells in a p-well. Very high α-particle immunity was achieved with this structure. One cell measures 3.0×5.8 µm2 yielding a chip size of 7.84 x 17.48 mm2. An on-chip voltage converter circuit was implemented as a mask option to investigate a possible solution to the MOSFET reliability problem caused by hot carriers. An 8-bit parallel test mode was introduced to reduce the RAM test time. Metal mask options provide static column mode and fast page mode operation. The chip is usable as ×1 or ×4 with a bonding option. Using an external 5-V power supply, the RAS access time is 80 ns at room temperature. Typical active current is 60 mA at a 220-ns cycle time with a standby current of 0.5 mA.
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