Abstract: A process for forming field oxide on a semiconductor substrate having reduced field oxide thinning comprises forming an oxide layer over a semiconductor substrate, and forming a protective layer over the oxide layer. A mask is formed over the protective layer thereby forming exposed and covered regions of the protective layer. The exposed portions of the protective layer are removed to form at least first, second, and third disconnected protective structures, wherein the distance between the first and second protective structures is smaller than the distance between the second and third protective structures. The oxide layer and a portion of the substrate between the protective structures is removed to expose a portion of the substrate. A blanket polycrystalline silicon (poly) layer is formed over the substrate, and the poly layer is isotropically etched to remove the poly from between the second and third protective structures and to leave a portion of the poly between the first and second structures.

Abstract: This invention constitutes a process for fabricating a structure which, when incorporated in an integrated circuit, will reduce current leakage into the substrate from transistor source/drain regions. The structure is particularly useful in dynamic random access memories, as it will minimize the effect of alpha particle radiation, thus improving the soft error rate. A trench is etched through the transistor source or drain region. A high dosage of oxygen ions is then implanted at low energy in the floor, but not the sidewalls of the trench. The resulting oxygen-implanted silicon layer at the bottom of the trench is then converted to a silicon dioxide barrier layer through rapid thermal processing or furnace annealing in an inert ambient. The trench is then lined with a deposited contact layer that is rendered conductive either during or subsequent to deposition. Contact between the contact layer and the source or drain region is made through the sidewalls of the trench, which were not implanted with oxygen.