We report, for the first time, excellent device characteristics of both n and p-channel (complementary) IGFETs with very thin nitride/oxide stacked gate insulators (10-14nm equivalent oxide thickness). The top nitride layer (as thin as 4nm) is effective in preventing boron penetration from the p+-poly gate to the channel. The threshold voltage instability and channel hot carrier effects are controlled by using (i) very thin top nitride (4nm), and (ii) complemetary gate work work functions, i.e., n+-poly for n-channel and p+-poly for p-channel IGFETs, respectively. Such composite insulators are very promising for submicron VLSI CMOS applications.