Abstract: A method of improving latch-up immunity and interwell isolation in a semiconductor device is provided. In one embodiment, an implant mask which has a variable permeability to implanted impurities is formed on the surface of a substrate having a first dopant region. A first portion of the implant mask overlies a first portion of the first dopant region. The structure is subjected to high energy implantation which forms a heavily doped region. A first portion of the heavily doped region is located along the lower boundary of the first dopant region. A second portion of the heavily doped region which extends along a side boundary of the first dopant region is formed by impurity ions which pass through the first portion of the implant mask. The heavily doped region improves latch-up immunity and interwell isolation without degrading threshold voltage tolerance.

Abstract: A structure for improving latch-up immunity and interwell isolation in a semiconductor device is provided. In one embodiment, a substrate has an upper surface and a first dopant region formed therein. The first dopant region has a lower boundary located below an upper surface of the substrate and a side boundary extending from the upper surface of the substrate to the lower boundary of the first dopant region. A heavily doped region having a first portion and a second portion located along the lower boundary and the side boundary of the first dopant region, respectively, has a substantially uniform dopant concentration greater than a dopant concentration of the first dopant region. The heavily doped region improves latch-up immunity and interwell isolation without degrading threshold voltage tolerance.

Abstract: For electrostatic-discharge-protection, a first transistor is configured with the transistor channel connected between circuit ground and an associated (input or output) pad. In addition, transistors(s) are included configured to "float" the gate and/or the well of the first transistor when no power supply potential (Vcc) is present and to couple to circuit ground (or the power supply potential) the gate and/or the well of the first transistor when the normal power supply potential (Vcc) is present.