Rabin & Champagne, P.C.
Process for fabricating a triple-well structure for semiconductor integrated circuit devices
 A triple-well structure for semiconductor IC devices such as an SRAM IC device and a process for its fabrication, that allows for improved data storage stability as well as improved immunity capability against interference from device I/O bouncing and alpha particles. The triple-well structure includes at least one P-well in a P-type substrate, a number of N-wells, and a retrograde P-well formed within one of the N-wells. The process for fabricating the triple-well structure includes first implanting boron ions in the P-type substrate. A photomask is subsequently formed for the implantation of phosphorous ions in the region where a P-type MOS transistor is to be fabricated. A high temperature drive-in procedure is then employed to form a P-well and a number of N-wells. A selected area of one of the N-wells where an N-type MOS transistor is defined is then subjected to boron ion implantation, which is followed by an annealing procedure to form the retrograde P-well. 
United Microelectronics Corp.
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H01L H01L
inventional inventional
Chung-Yuan Chen-Chiu Chun-Yen Sun-Chieh
Lee Hsu Chang Chien