Abstract: A series of oxide growth and etch-back operations is employed to form the isolation region of an MOS device (10). The series of operations forms an oxidation susceptible layer (14) into oxidation resistant areas (21) and oxidation susceptible areas (19) thereby confining the effects of a thermal oxidation procedure to the oxidation susceptible areas (19) of the MOS device (10). The thickness of both the oxidized (19) and non-oxidized regions (21) is reduced. Another oxidation is performed and the oxidized material (19, 21) is thinned.

Abstract: A process for fabricating high-capacitance trench capacitors in a lightly doped, shallow well of a semiconductor substrate. The process involves a two-step doped glass deposition/diffusion routine. After trench formation into a shallow, lightly doped well, a first doped glass is deposited inside the trench and the dopant is diffused from the glass through the trench interior surface to form a region or halo of extra doping around and below each trench. A second doped glass deposition and diffusion of an impurity of the opposite conductivity type to a shallow depth on the trench wall surfaces provides a p/n junction with the first diffusion region to increase the capacitance of the subsequent capacitor. In addition, the trench devices are better isolated from each other, the substrate and any adjacent devices.

Abstract: A bulge well structure for trench devices in wells of a conductivity type opposite to that of the substrate where the bottom of the trench has localized, extra doping. The additional doping into the bottom of the trench prior to device formation may be implanted while the photoresist mask for the trench formation is still in place. In one embodiment of the method, the trenches and the bulge or well extension formations at their bottoms are created before isolation regions are formed. The structure and method permit increased doping only where needed and are compatible with thin epitaxial layers and sharp transition interfaces of epitaxy with substrate for optimum latchup protection. No extra masks are required and the tight packing allowed by trench technology is not altered. Protection against soft errors and junction leakage by forming DRAM trench capacitors in a well of opposite conductivity type from the substrate may be provided.

Abstract: A process for forming a DRAM cell having a capacitor adjacent a field effect transistor (FET), wherein the FET fabrication area is protected from adverse effects of the capacitor formation. The process is misalignment tolerant and provides FETs with appreciably lower defects in the substrate beneath the FET. Additionally, the process eliminates the need to stop an etching operation on a thin capacitor dielectric layer.