Semiconductor device capable of enhancing a withstand voltage at a peripheral region around an element in comparison with a withstand voltage at the element

A semiconductor device comprising:

• an element region formed on a substrate having a semiconductor layer with a first conductivity;
• a guard ring region with a second conductivity formed in the semiconductor layer, located at a periphery of the element region;
• a connecting region with the second conductivity formed in the semiconductor layer so as to contact with the guard ring region, the connecting region having higher impurity concentration in comparison with the guard ring region, and the connecting region being not completely depleted at a surface portion thereof when the breakdown occurs at the cell region;
• an electrode contacting with the connecting region, for applying a reverse bias to a pn junction formed between a portion with the first conductivity and a portion with the second conductivity in the substrate, wherein when the reverse bias is applied to the pn junction, the guard ring region is completely depleted while the connecting region is partially depleted so as to form a depletion portion and a carrier remaining portion disposed on the depletion region;
• and
• a step formed at a surface portion of the substrate so as to terminate an upper limit side of the depletion portion at a contour thereof which is disposed lower than a standard plane of the substrate.

A semiconductor device comprising:

• a substrate;
• a cell region formed on the substrate, acting as a device and having well regions therein that have a second conductive type;
• a guard ring region formed at a periphery of the cell region in the substrate, having the second conductive type so as to define a pn junction with the substrate;
• a connecting region located between the guard ring region and at least one of the well regions so as to connect the guard ring region to the at least one of the well regions, the connecting region having the second conductive type;
• a step formed approximately at a boundary portion that is formed between the guard ring region and the connecting region so that the impurity diffused guard ring is disposed at a lower portion thereof and the connecting impurity diffused region is disposed at a higher portion that is higher than the lower portion with a wall portion interposed therebetween so that the guard ring region is located at the lower portion.