ABSTRACT
Since its invention in the early 1960s, metal oxide silicon field effect transistor (MOSFET) [1] has been the building block of one of the world’s biggest industries, the semiconductor industry. The semiconductor industry has become the most important engine driving the world economy and has distinguished itself by the rapid pace of improvement in its products over the past four decades. The improvement trend in the integration level is usually expressed as “Moore’s law”: the number of components per chip doubles every 2 years since about 1980 [2-4]. This remarkable achievement is attributed to the progress in device scaling that has followed an exponential curve. The minimum feature size in recent complementary metal-oxidesilicon (CMOS) technology is beginning to touch the sub-50 nm ranges. The most recent International Technology Roadmap for Semiconductors (ITRS) has forecast a device gate length as short as about 25 nm by 2015 [2]. The technology leading devices in minimum feature size are, without a doubt, memory products such as dynamic random access memory (DRAM).
