Semiconductor device having impurity regions with varying impurity concentrations

摘要

In an access transistor formed on a silicon substrate, its drain region is formed of n- type and n+ type drain regions and its source region is formed of n- type and n+ type source regions. In a driver transistor, its source region is formed of n- type and n++ type source regions and its drain regions is formed of n- type and n+ type drain regions. The n+ +type source region is formed deeper than the n+ type drain region. Accordingly, a semiconductor device ensuring improvement in a static noise margin while suppressing increase in manufacturing cost is provided.