Semiconductor trench capacitor structure and manufacturing method thereof

A semiconductor structure, comprising:

• a semiconductor substrate defining a trench, the trench including a top portion having a top width, a bottom portion having a bottom width, and two sidewalls beneath the top portion and perpendicular to the semiconductor substrate, wherein the top width is less than the bottom width;
• a protection dielectric layer overlying a top surface of the semiconductor substrate and the two sidewall surfaces of the trench;
• and
• a trench capacitor disposed over the semiconductor substrate and filling the trench, wherein the trench capacitor comprises:
• a first trench electrode layer overlying the semiconductor substrate and lining the trench;
• a capacitor dielectric layer overlying the first trench electrode layer and lining the trench over the first trench electrode layer;
• and
• a second trench electrode layer overlying the capacitor dielectric layer and filling the trench over the capacitor dielectric layer,
• wherein the protection dielectric layer has a thinnest thickness greater than a thinnest thickness of the first trench electrode layer or the second trench electrode layer, and
• wherein the first trench electrode layer is in direct contact with the semiconductor substrate.

A method of forming a semiconductor device, the method comprising:

• providing a semiconductor substrate;
• performing an etch into the semiconductor substrate to form a trench, wherein the trench includes a top portion having a top width, a bottom portion having a bottom width, and two sidewalls beneath the top portion and perpendicular to the semiconductor substrate, wherein the top width is less than the bottom width;
• forming a protection dielectric layer overlying a top surface of the semiconductor substrate and the two sidewall surfaces of the trench;
• and
• forming a layer stack including at least two trench electrode layers interlaced with a capacitor dielectric layer over the semiconductor substrate and filling the trench;
• wherein the protection dielectric layer has a thickness greater than a half of a thinnest thicknesses of the at least two trench electrode layers, and
• wherein the lower trench electrode layer is in direct contact with the semiconductor substrate.