Patent ID: 7659581
Filing Date: 2010-02-09
Classification: H01L

Abstract:
1. A chip, comprising: a first semiconductor region; an active semiconductor region overlying the first semiconductor region, said active semiconductor region having a top surface, a bottom surface and edges extending between the top and bottom surfaces; a p-type field effect transistor (“PFET”) having a channel region, a source region and a drain region all disposed within said active semiconductor region, and a dielectric stressor element disposed between the bottom surface of the active semiconductor region and the first semiconductor region, the dielectric stressor element including a buried oxide region separating an entirety of the active semiconductor region from the first semiconductor region; a trench isolation region having walls, wherein the buried oxide region and said edges of said active semiconductor region contact the walls of the trench isolation region; and bird's beak oxide regions disposed between the first semiconductor region and a bottom surface of the buried oxide region, the bird's beak oxide regions formed by local oxidation of semiconductor material and extending laterally inward from the walls of the trench isolation region below the buried oxide region, such that the bird's beak oxide regions become thinner the farther the bird's beak oxide regions extend from the walls of the trench isolation region until the bird's beak oxide regions end in tips underlying the buried oxide region, the bird's beak oxide regions causing the top surface of the active semiconductor region to bend upwardly at said edges and apply a compressive stress to said channel region of said PFET, wherein said bird's beak oxide regions are first bird's beak oxide regions, said chip further comprising second bird's beak oxide regions disposed between a top surface of the buried oxide region and the bottom surface of the active semiconductor region, the second bird's beak oxide regions formed by local oxidation of semiconductor material and extending laterally inward from the walls of the trench isolation region above the buried oxide region, such that the second bird's beak oxide regions become thinner the farther the second bird's beak oxide regions extend from the walls of the trench isolation region until the second bird's beak oxide regions end in tips overlying the buried oxide region.