Metal oxide semiconductor capacitors having uniform C-V characteristics over an operating range and reduced susceptibility to insulator breakdown

摘要

A MOS capacitor has uniform C-V capacitance characteristics across an operating voltage range and has reduced susceptibility to insulator breakdown and includes a semiconductor substrate of first conductivity type, a region of insulating material on an upper surface of the substrate and a well region of second conductivity type extending adjacent the region of insulating material. The well region is spaced from the region of insulating material so that the substrate extends to the upper surface therebetween. A source region of second conductivity type is formed in the well region. An insulating layer is formed on the source region and extends over the region of insulating material. A first electrode is formed on the insulating layer and a second electrode is formed on the source region. The capacitor also includes a P-N junction established between the source region of second conductivity type and the region of insulating material beneath the insulating layer. This P-N junction provides the capacitor with substantially uniform capacitance characteristics when a voltage is applied between the first electrode and the second electrode. Furthermore, because some of the voltage differential is established across the P-N junction during operation, the electric field at the corner of the region of insulating material and the insulating layer is reduced.