Solid-state image sensor and imaging system

A method of formation of a solid state image sensor comprising:

• forming at least one source-drain region of MOS transistors;
• forming a first layer on the at least one source drain region;
• forming a plurality of insulating layers and a plurality of wiring layers, wherein the wiring layer furthest from the first layer is referred to as the outer wiring layer;
• planarizing at least one of the insulating layers;
• forming a plasma CVD layer above the outer wiring layer;
• heating the plasma CVD layer at a target temperature in a target environment for a target period of time;
• and
• forming an optical element on the plasma CVD layer.