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:
an active area containing transistor cells;
a gate metal area containing no transistor cells; and
a gate metal layer,
wherein a trench is formed in a pattern on a surface of the semiconductor chip, the trench extending from the active area into the gate metal area, the trench having walls lined with a layer of an insulating material, a conductive gate material being disposed in the trench, a top surface of the conductive gate material being at a level below a top surface of the semiconductor chip, a nonconductive layer overlaying the active and gate metal areas, an aperture being formed in the nonconductive layer over a portion of the trench in the gate metal area, the aperture being filled with a gate metal such that the gate metal contacts the gate material in an area of contact within the trench and wherein a first gate finger extends from the active area to the gate metal area. the area of contact between the gate contact material and the conductive gate material being located in a second gate finger, the second gate finger being perpendicular to the first gate finger.
2. The trench-gated MIS device of claim 1 comprising a gate metal layer overlying the nonconductive layer in the gate metal area, the gate metal layer being in electrical contact with the 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 the trench in the gate metal area.
4. The trench-gated device of claim 1 wherein a width of the second gate finger is the same as a width of the first gate finger at an intersection between the first and second gate fingers.
5. A trench-gated MIS device formed in a semiconductor chip and comprising:
an active area containing transistor cells;
a gate metal area containing no transistor cells;
a first and a second gate finger extending from the active area to the gate metal area; and
a gate metal layer,
wherein a trench is formed in a pattern on a surface of the semiconductor chip, the trench extending from the active area into the gate metal area, the trench having walls lined with a layer of an insulating material, a conductive gate material being disposed in the trench, a top surface of the conductive gate material being at a level below a top surface of the semiconductor chip, a nonconductive layer overlaying the active and gate metal areas, an aperture being formed in the nonconductive layer over a portion of the trench in the gate metal area, the aperture being filled with a gate metal such that the gate metal contacts the gate material in an area of contact within the trench.
6. The trench-gated MIS device of claim 5 comprising a gate metal layer overlying the nonconductive layer in the gate metal area, the gate metal layer being in electrical contact with the gate material.
7. The trench-gated MIS device of claim 6 wherein the gate metal layer extends longitudinally in a direction perpendicular to a direction of the trench in the gate metal area.