Electrical performance and reliability of a semiconductor device comprising continuous diffusion structures

A semiconductor device includes a core gate and a pair of isolation gates. The core gate has a first stack of two or more layers, the first stack including at least (i) a first dielectric layer having a first thickness and (ii) a first electrode layer. The isolation gates are formed on first and second sides of the core gate. The isolation gates are configured to electrically isolate the core gate. At least one of the isolation gates has a second stack of two or more layers, the second stack including at least (i) a second dielectric layer having a second thickness greater than the first thickness and (ii) a second electrode layer.