Enhancement of stress-memorization technique on nMOSFETs by multiple strain-gate Engineering

An enhanced stress memorization-technique that utilizes a strain proximity free technique (SPFT) and a stacked-gate structure has been demonstrated by multiple strain-gate engineering. The electron mobility of n-channel metal-oxide semiconductor field effect transistors (nMOSFETs) with SPFT exhibit a 16% increase compared to that of counterpart techniques. SPFT avoids the limitation of stressor volume for performance improvement in high-density complementary metal oxide semiconductor circuits. We also found that optimization of stacked, random poly-Si-grain gate structure in combination with SPFT can improve mobility further to 22% more than a single poly-Si gate structure without SPFT.