Abstract: An n type impurity region is continuously formed on the bottom portion of a channel region below a source region, a gate region and a drain region. The n type impurity region has an impurity concentration higher than the channel region and a back gate region, and is less influenced by the diffusion of p type impurities from the gate region and the back gate region. Moreover, by continuously forming the impurity region from a portion below the source region to a portion below the drain region, the resistance value of a current path in the impurity region is substantially uniformed. Therefore, the IDSS is stabilized, the forward transfer admittance gm and the voltage gain Gv are improved, and the noise voltage Vno is decreased. Furthermore, the IDSS variation within a single wafer is suppressed.

Abstract: In the semiconductor device, a gate region is formed in a mesh pattern having first polygonal shapes and second polygonal shapes the area of which is smaller than that of the first polygonal shapes, and drain regions and source regions are disposed within the first polygonal shapes and the second polygonal shapes, respectively. With this configuration, the forward transfer admittance gm can be increased as compared with a structure in which gate regions are disposed in a stripe pattern. Furthermore, compared with a case in which a gate region is disposed in a grid pattern, deterioration in forward transfer characteristics (amplification characteristics) due to an increase in input capacitance Ciss can be minimized while a predetermined withstand voltage is maintained.

Abstract: An n type impurity region is continuously formed on the bottom portion of a channel region below a source region, a gate region and a drain region. The n type impurity region has an impurity concentration higher than the channel region and a back gate region, and is less influenced by the diffusion of p type impurities from the gate region and the back gate region. Moreover, by continuously forming the impurity region from a portion below the source region to a portion below the drain region, the resistance value of a current path in the impurity region is substantially uniformed. Therefore, the IDSS is stabilized, the forward transfer admittance gm and the voltage gain Gv are improved, and the noise voltage Vno is decreased. Furthermore, the IDSS variation within a single wafer is suppressed.

Abstract: In the semiconductor device, a gate region is formed in a mesh pattern having first polygonal shapes and second polygonal shapes the area of which is smaller than that of the first polygonal shapes, and drain regions and source regions are disposed within the first polygonal shapes and the second polygonal shapes, respectively. With this configuration, the forward transfer admittance gm can be increased as compared with a structure in which gate regions are disposed in a stripe pattern. Furthermore, compared with a case in which a gate region is disposed in a grid pattern, deterioration in forward transfer characteristics (amplification characteristics) due to an increase in input capacitance Ciss can be minimized while a predetermined withstand voltage is maintained.