Abstract: A memory device and its manufacturing method are provided, including: a semiconductor substrate, including a shallow trench isolation structure and an active area positioned at one side of the shallow trench isolation structure; two buried word lines and a first dielectric layer, wherein the buried word lines are disposed in the semiconductor substrate and separated from each other, the first dielectric layer is disposed on the semiconductor substrate and corresponds to the two buried word lines; a contact plug disposed on the semiconductor substrate and within the active area, including a conductive layer and an epitaxial layer, the conductive layer is disposed on the sidewalls of the first dielectric layer, the epitaxial layer is disposed on the sidewalls of the conductive layer and extends into the semiconductor substrate; a second dielectric layer disposed over the semiconductor substrate, covering the contact plug and the shallow trench isolation structure.

Abstract: A memory device and its manufacturing method are provided, including: a semiconductor substrate, including a shallow trench isolation structure and an active area positioned at one side of the shallow trench isolation structure; two buried word lines and a first dielectric layer, wherein the buried word lines are disposed in the semiconductor substrate and separated from each other, the first dielectric layer is disposed on the semiconductor substrate and corresponds to the two buried word lines; a contact plug disposed on the semiconductor substrate and within the active area, including a conductive layer and an epitaxial layer, the conductive layer is disposed on the sidewalls of the first dielectric layer, the epitaxial layer is disposed on the sidewalls of the conductive layer and extends into the semiconductor substrate; a second dielectric layer disposed over the semiconductor substrate, covering the contact plug and the shallow trench isolation structure.

Abstract: A semiconductor device is provided, including a substrate; a dielectric structure over the substrate; and a capping layer over the dielectric structure. The bottom of the capping layer has an M-shaped cross section. The capping layer and the dielectric structure are formed of different materials.