TW289862B - High-density mask ROM device and process thereof - Google Patents

Abstract

A process of high-density mask ROM device, which is applicable to one silicon substrate, comprises of: (1) via mask patterning performing one ion implantation procedure to form multiple thickly doped source/drain region in the substrate, and forming multiple bit lines extending with one first direction; (2) performing one chemical vapor deposition procedure to form first gate oxide with width at least 500 A on the silicon substrate, and extending with one second direction, and forming transistor channel in silicon substrate between every two joining bit lines under the first gate oxide; (3) via mask patterning one coding region, etching the first gate oxide, making the silicon substrate surface above transistor channel of the coding region expose; (4) performing one oxidization procedure to form one second gate oxide on silicon substrate surface of the coding region with the second gate oxide thickness between 100 A to 300 A; and (5) forming one conductive layer on the gate oxide, and etching back to form multiple gate electrode, forming multiple word lines extending with second direction; in which the transistor channel, two source/drain region connecting to the transistor channel, the gate oxide on the transistor channel and the gate electrode commonly forms one memory cell, by thickness difference of the gate oxide making transistor channel of the memory cells form OFF and ON two states.