Abstract: A semiconductor structure having an improved polysilicon layer is formed. After the formation of a silicon dioxide layer over a semiconductor wafer, the semiconductor wafer is heated in an ambient comprised of nitrogen. The heating is preferably accomplished so that nitridation of the silicon dioxide does not take place. Subsequently, a polysilicon layer is formed on the silicon dioxide layer. The polysilicon layer is denser and thus more resistant to hydrogen fluoride than polysilicon formed without exposing the silicon dioxide layer to nitrogen.

Abstract: A method of selectively forming a field oxide in a semiconductor device is provided by implanting a dopant into selected regions of a semiconductor substrate. A high concentration of dopant provides for an enhanced oxide growth rate. Another dopant may be implanted if necessary to provide a high field threshold voltage to prevent inversion. Annealing the semiconductor substrate and growing the oxide at a predetermined temperature will keep the high concentration of dopant in the semiconductor substrate, and thus maintain a state of enhanced oxide growth throughout the oxidation cycle. By taking advantage of enhanced oxidation, a mask, such as silicon nitride, is not required to prevent the substantial growth of oxide in the undoped region or active area.

Abstract: A simplified process is used to obtain pattern delineation for a buried layer by making use of the metastable state of silicon to grow oxide at different rates on the surface of the silicon. A silicon substrate having dopants implanted in a predetermined location is annealed at a low temperature. Oxide is then grown on the surface of the substrate at a temperature which maintains the silicon in a metastable state. The oxide will grow faster over the doped region than it will over the undoped region thereby providing a step which can be used for pattern delineation. After the oxide is grown the substrate is diffused in order to drive the impurity to the desired depth.