CMOS image sensors having a transfer gate electrode, and methods of fabricating CMOS image sensors having a transfer gate electrode

A complementary metal-oxide-semiconductor (CMOS) image sensor comprising:

• a substrate including a pixel array and a peripheral circuit region;
• a photodiode and a floating diffusion region in the pixel array of the substrate;
• a transfer gate insulating layer and a transfer gate electrode on a portion of the substrate that is between the photodiode and the floating diffusion region;
• and
• a peripheral gate insulating layer and a peripheral gate electrode on the peripheral circuit region,
• wherein the transfer gate electrode includes a first edge that is rounded to have a first radius of curvature,
• wherein the peripheral gate electrode includes a second edge that is rounded to have a second radius of curvature shorter than the first radius of curvature, and
• wherein the transfer gate electrode further comprises a third edge that is rounded to have a third radius of curvature shorter than the first radius of curvature.