SEMICONDUCTOR DEVICE AND ITS MANUFACTURE

摘要

PURPOSE: To provide a semiconductor device structure which is formed by using a polycrystalline layer which is mainly aligned in specified crystal face orientation, and a specified means. CONSTITUTION: A layer 3 is formed in which the impurity concentration in the vicinity of the interface 30 of a base film 2 on a substrate l is controlled to be extremely low (infinitely close to zero) as compared with that of the film inside or to be sufficiently high. Thereby the crystal face orientation after a silicon layer 4 is crystallized is aligned mainly in specified crystal face orientation, so that mechanical characteristics like the internal stress of a thin film and electric characteristics of a semiconductor element formed in each crystal grain of polycrystalline silicon are improved. The thickness of a silicon thermal oxidation film formed by oxidizing the surface of the polycrystalline silicon thin film can be made uniform. Since the orientation of a crystal face can be controlled in the specified crystal face direction, an uniform polycrystalline layer wherein the value of internal stress is controlled can be stably obtained.