NOVELTY - Forming epitaxial thin film (1075) comprises: providing assembly substrate (1030) with many openings that defines first pattern for epitaxial layer; directing liquid phase epitaxial material into openings; maintaining crystalline seed substrate in fixed contact with assembly substrate for at least first duration in which the material is introduced into openings; arranging assembly substrate and seed substrate so that epitaxial layer growth is initiated at surface region of seed substrate situated at bottom of openings and controlled until epitaxial layer is formed within first pattern.    USE - The method is useful: for forming epitaxial thin film which forms part of a p-n junction and an integrated circuit device and active devices on the assembly substrate and/or the thin film epitaxial layer (all claimed); and to form solar cell, LED devices and assembled into higher integration of desired applications comprising monolithic devices, chip scale packaging and multi component modules and devices with double or multi junction.    ADVANTAGE - The method: provides layers and structures that are freely separated from seed substrates and allows reusing substrates and ease of later processing for additional active devices; saves package and assembly costs, operational steps and costs in wafer mount, wafer thinning, wafer dicing, and die attach, replaces semiconductor substrate with low cost assembly substrate and liquid phase epitaxial material, thus cost effective; provides epitaxial layer in high yields with high material quality for wide applications; does not adopts fabrication of inverted device structure; provides transformational epitaxy-level packaging technique that advances beyond chip-scale packaging, wafer-level packaging; and is easily integrable in liquid phase epitaxy equipment for high throughput.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of growth of epitaxy layer on crystalline substrate and assembly substrate.    Crystalline substrate (1010)    Sacrificial layer (1020)    Assembly substrate (1030)    Plate (1038)    Epitaxial film (1075)