Semiconductor device and manufacturing method thereof

摘要

A conventional DRAM needs to be refreshed at an interval of several tens of milliseconds to hold data, which results in large power consumption. In addition, a transistor therein is frequently turned on and off; thus, deterioration of the transistor is also a problem. These problems become significant as the memory capacity increases and transistor miniaturization advances. A transistor is provided which includes an oxide semiconductor and has a trench structure including a trench for a gate electrode and a trench for element isolation. Even when the distance between a source electrode and a drain electrode is decreased, the occurrence of a short-channel effect can be suppressed by setting the depth of the trench for the gate electrode as appropriate.

主权项

1. A semiconductor device comprising:
a semiconductor substrate; a first trench in the semiconductor substrate; an impurity region in the semiconductor substrate; a first insulating layer in contact with an inner wall surface of the first trench; a first gate electrode in the first trench and over the first insulating layer; a second insulating layer over the first gate electrode and the semiconductor substrate; a third insulating layer over the second insulating layer; an oxide semiconductor layer over and in contact with the third insulating layer; a fourth insulating layer over and in contact with the oxide semiconductor layer; and a second gate electrode adjacent to the oxide semiconductor layer with the fourth insulating layer provided therebetween.