Semiconductor device including image pick up device

Abstract

The performance of a semiconductor device is improved by preventing 1/f noise from being generated in a peripheral transistor, in the case where the occupation area of photodiodes, which are included in each of a plurality of pixels that form an image pickup device, is expanded. In the semiconductor device, the gate electrode of an amplification transistor is formed by both a gate electrode part over an active region and a large width part that covers the boundary between the active region and an element isolation region and the active region near the boundary and that has a gate length larger than that of the gate electrode part.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor device comprising steps of:
 providing a photoelectric conversion element that generates a signal electric charge in accordance with a light amount of incident light;   providing a forwarding transistor that forwards the signal electric charge to a charge detector;   providing an amplification transistor that outputs an electric signal corresponding to a potential variation in the charge detector;   providing a resetting transistor that resets a potential of the charge detector to a predetermined value; and   providing a selection transistor that externally outputs the electric signal output from the amplification transistor,   wherein a first gate electrode of the amplification transistor and a second gate electrode of the selection transistor, which cross over an active region surrounded by an element isolation region, are formed in the active region, and   wherein in a portion immediately above the active region, a gate length of at least one end portion in a gate width direction of the first gate electrode is larger than that of a central portion in the gate width direction of the first gate electrode.   
     
     
         2 . The method of manufacturing a semiconductor device according to  claim 1 ,
 wherein in a portion immediately below the first gate electrode, a diffusion layer, having the same conductive type as that of a channel region of the amplification transistor, is formed in the active region adjacent to the element isolation region.   
     
     
         3 . The method of manufacturing a semiconductor device according to  claim 2 ,
 wherein in a portion immediately below the second gate electrode, a diffusion layer, having the same conductive type as that of a channel region of the selection transistor, is formed in the active region adjacent to the element isolation region.