NOVELTY - The method involves generating plasma containing reactive gas ions in a plasma chamber (102). A plasma sheath modifier (PSM) (126) including an aperture placed between plasma (302) and a substrate (118) is provided to direct reactive gas ions toward the substrate. Bias voltage is generated between the substrate and the plasma chamber. Pressure differential between the plasma chamber and a substrate region is established, while the reactive gas ions are directed toward the substrate. Temperature gradient is provided in a plane of the substrate.    USE - Method for ion-assisted processing a substrate for industrial applications. Uses include but are not limited to micro-electrical mechanical devices (MEMS), solar cell devices, electronic sensors, transducers, memory devices and magnetic devices.    ADVANTAGE - The method enables patterning the substrate to form patterned deposition on the substrate or patterned etching of the substrate in a less complex and cost effective manner. The method enables enhancing ability to direct localized processing in a desired local area of the substrate without incurring unwanted processing in other areas of the substrate. The method enables improving the patterning of the substrate by providing local deposition or local etching on the substrate to provide corresponding pattern of deposited material or etched portions in the substrate. The method enables improving three dimensional (3D) deposition, 3D doping, 3D etching and 3D precision material modification. The method enables minimizing relative effect of impingement of reactive gas neutrals as compared to the depositing ions and the etching ions. The method enables fabricating structures and devices, thus eliminating complex lithographic processing employed to pattern the substrate. The method enables avoiding elimination of lithographic patterning steps, etching, cleaning and related processes, thus reducing manufacturing complexity and cost.    DETAILED DESCRIPTION - The plasma containing reactive gas ions are silane based plasmas. The reactive gas ions are deposited on material that is selected from a group consisting of elemental semiconductor, compound semiconductor, oxide, nitride, carbide, suicide, ternary compound, elemental metal, metallic compound, metallic alloy, polymeric material and composite material. An INDEPENDENT CLAIM is also included for a system for processing a substrate.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a structure with varying deposit width of deposited material during ion-assisted localized deposition in a processing system.    Plasma chamber (102)    Substrate (118)    PSM (126)    Plasma sheath (204)    Plasma (302)