Semiconductor device with less power supply noise

Abstract

A semiconductor device includes a first power supply line; a second power supply line; a first cell arrangement area in which a first cell is arranged; and a switch area in which a switching transistor and a decoupling capacitance are arranged. The first cell is provided in a first well of a first conductive type, the switching transistor is provided in a second well of the first conductive type, and the decoupling capacitance is provided in a separation area of a second conductive type to separate the first well and the second well from each other. The switching transistor connects the first power supply line and the second power supply line in response to a control signal, the first cell operates with power supplied from the second power supply line, and the decoupling capacitance is connected with the first power supply line.

What is claimed is: 
     
         1 . A semiconductor device comprising:
 a power supply line used to supply a power supply voltage;   a ground line used to supply a ground voltage;   a disconnection possible power supply line;   a switch configured to supply said power supply voltage to said disconnection possible power supply line in response to a control signal;   a first standard cell configured to operate based on said power supply voltage supplied from said disconnection possible power supply line;   a second standard cell arranged between said power supply line and said ground line to operate without depending on the operation of said switch; and   a capacitor provided near to said switch between said power supply line and said ground line.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein said capacitor supplies stored electric charge when said switch connects said power supply line and said disconnection possible power supply line.