BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor memory device and a manufacturing method thereof, and more particularly, to a semiconductor memory device including a semiconductor active structure disposed in a trench and a manufacturing method thereof.

2. Description of the Prior Art

Semiconductor memory devices are used in computer and electronics industries as a means for retaining digital information or data. Typically, the semiconductor memory devices are divided into volatile and non-volatile memory devices. The non-volatile memory devices, which can retain data even when the power supply is interrupted, have been widely employed. As one kind of the non-volatile memory technology, a SONOS memory structure is to build a silicon nitride layer sandwiched between two silicon oxide layers for serving as the charge trapping layer while the two silicon oxide layers respectively serve as a charge tunnel layer and a charge block layer. This oxide-nitride-oxide (ONO) multilayered structure is disposed on a semiconductor substrate, a silicon floating gate may be disposed on the ONO multilayered structure, and thus a SONOS memory structure is constructed.

Since the microprocessors have become more powerful, requirement to memory devices of large-capacity and low-cost is raised. To satisfy such trend and achieve challenge of high integration in semiconductor devices, memory miniaturization is kept on going, and thus fabrication process of memory structure is getting complicated. It is difficult to effectively enhance the manufacturing yield because of many issues occurred correspondingly.

SUMMARY OF THE INVENTION

A semiconductor memory device and a manufacturing method thereof are provided in the present invention. A semiconductor active structure is formed in a trench penetrating through an isolation layer for avoiding an influence of an edge shape of a shallow trench isolation structure formed in a semiconductor material on a formation of a floating gate electrode formed subsequently, and the purpose of manufacturing yield enhancement may be achieved accordingly.

According to an embodiment of the present invention, a semiconductor memory device is provided. The semiconductor memory device includes a substrate, an isolation layer, a trench, a semiconductor active structure, and a floating gate electrode. The isolation layer is disposed on the substrate. The trench penetrates through the isolation layer and exposes a part of the substrate. The semiconductor active structure is disposed in the trench. The floating gate electrode is disposed on the semiconductor active structure.

According to an embodiment of the present invention, a manufacturing method of a semiconductor memory device is provided. The manufacturing method includes the following steps. An isolation layer is formed on a substrate. A trench is formed penetrating through the isolation layer and exposing a part of the substrate. A semiconductor active structure is formed in the trench. A floating gate electrode is formed on the semiconductor active structure.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

