Structures of and methods of fabricating trench-gated MIS devices
View Patent ↗In a trench-gated MIS device contact is made to the gate within the trench, thereby eliminating the need to have the gate material, typically polysilicon, extend outside of the trench. This avoids the problem of stress at the upper corners of the trench. Contact between the gate metal and the polysilicon is normally made in a gate metal region that is outside the active region of the device. Various configurations for making the contact between the gate metal and the polysilicon are described, including embodiments wherein the trench is widened in the area of contact. Since the polysilicon is etched back below the top surface of the silicon throughout the device, there is normally no need for a polysilicon mask, thereby saving fabrication costs.
1. A trench-gated MIS device formed in a semiconductor chip and comprising:
a first active area and a second active area each comprising transistor cells;
a gate metal area containing no transistor cells; and
a gate metal layer,
wherein a plurality of trenches are formed in a pattern on a surface of the semiconductor chip, each trench extending from the first active area to the second active area and passing through the gate metal area, each trench having walls lined with a layer of an insulating material, a conductive gate material being disposed in each trench, a top surface of the conductive gate material being at a level below a top surface of the semiconductor chip, a nonconductive layer overlying the active and gate metal areas, a plurality of apertures being formed in the nonconductive layer, each aperture being formed over a portion of a respective trench in the gate metal area such that each aperture is spaced apart from each other, each aperture being filled with the gate metal layer such that the gate metal layer contacts the conductive gate material in an area of contact within each trench.
2. The trench-gated MIS device of claim 1 wherein said gate metal layer overlies the nonconductive layer in the gate metal area, the gate metal layer being in electrical contact with the conductive gate material.
3. The trench-gated MIS device of claim 2 wherein the gate metal layer extends longitudinally in a direction perpendicular to a direction of each trench in the gate metal area.
4. The trench-gated MIS device of claim 1 wherein a width of each trench at the area of contact between the gate metal layer and the conductive gate material is greater than a width of each trench in the first and second active areas.