Geometry-controllable design blocks of MOS transistors for improved ESD protection

摘要

An MOS transistor in the surface of a semiconductor substrate (180) of a first conductivity type, which has a grid of isolations (171) in the surface, each grid unit surrounding a rectangular semiconductor island (102). Each island contains three parallel regions of the opposite conductivity type: the center region (104) is operable as the transistor drain and the two other regions (103 and 105), abutting the isolations, are operable as transistor sources. Transistor gates (106 and 107) are between the parallel regions, completing the formation of two transistors having one common drain. Electrical contacts (108) are placed on both source regions and the drain region. The source contacts are placed so that the spacing (120) between each contact and its respective isolation is at least twice as large as the spacing (121) between each contact and the gate. A plurality of these islands are interconnected to form a multi-finger MOS transistor having increased ESD failure threshold current by spreading the power dissipation and thus reducing the current localization without impacting the drain-to-substrate capacitance.