NOVELTY - The emitter region comprises: a portion of a N-type bulk silicon substrate (102) having a back surface (106) opposite to a front surface and a light receiving surface; a silicon oxynitride (SiOxNy, where x and y is greater than 0) dielectric layer (108) disposed on the back surface of the portion of the substrate, where the silicon oxynitride dielectric layer has a non-homogeneous distribution of nitrogen; and a semiconductor layer (110) disposed on the silicon oxynitride dielectric layer. The front surface is a light receiving surface of a solar cell.    USE - The emitter region is useful in a solar cell (claimed).    ADVANTAGE - The emitter region improves the efficiency of the solar cell, and reduces the manufacturing cost of the solar cell.    DETAILED DESCRIPTION - The emitter region comprises: a portion of a N-type bulk silicon substrate (102) having a back surface (106) opposite to a front surface and a light receiving surface; a silicon oxynitride (SiOxNy, where x and y is greater than 0) dielectric layer (108) disposed on the back surface of the portion of the substrate, where the silicon oxynitride dielectric layer has a non-homogeneous distribution of nitrogen; and a semiconductor layer (110) disposed on the silicon oxynitride dielectric layer. The front surface is a light receiving surface of a solar cell. The dielectric layer has two nitrogen concentration maxima, where one of the maxima is at a surface of the silicon oxynitride dielectric layer proximate to the back surface of the portion of the substrate, and other of the maxima is at a surface of the silicon oxynitride dielectric layer distal from the back surface of the portion of the substrate. The distance between the maxima is 5-6 Angstrom . The dielectric layer has: a thickness of 10-20 Angstrom ; has a first nitrogen-rich region having a thickness of 4-5 Angstrom , a first nitrogen-poor region disposed above the first nitrogen-rich region and having a thickness of 5-6 Angstrom , and a second nitrogen-rich region disposed above the first nitrogen-poor region and having a thickness of 4-5 Angstrom ; and has a composition. The semiconductor layer disposed on the dielectric layer is a boron-doped silicon layer. The dielectric layer: inhibits dopant penetration from the semiconductor layer to the portion of the substrate; and is a silicon oxynitride tunnel dielectric layer for the emitter region. The emitter region further comprises a metal contact disposed on the semiconductor layer. An INDEPENDENT CLAIM is included for a solar cell.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic cross sectional view of an emitter region of a solar cell.    N-type bulk silicon substrate (102)    Back surface of portion of substrate (106)    Silicon oxynitride dielectric layer (108)    Nitrogen concentration maxima (108A)    Semiconductor layer. (110)