Smallest p-n-p-n memory cell

Although the p-n-p-n device is suitable for a 1-bit/cell static mamory, it has not yet been put to practical use because of its large cell size. By employing a sophisticated process involving single-crystal/poly-Si simultaneous growth on the same substrate, the smallest-sized vertical p-n-p-n device has been developed. Using this cell structure, a 12-bit scanner with 21.2-MHz transfer frequency, 16-µm pitch and 10-µmW/bit power dissipation has been fabricated. This cell structure is also applied to a static RAM with 22 × 27 = 594 µm²cell size. A high switching speed as well as a high packing density is predicted by this configuration.