my project use the mosfet as preventing inrush current，it been serial in the main board，as below
now，the vds value of Part of the chip increase， result in the main board supply voltage decrease and can't run normally；
my customer cut the fault chip ，and photograph the internal circuit，the photo as below。
figure1
figure 2
the figure 1 is the cross-section draw of the fault chip internal circuit ，figure2 is the good chip cross-section draw。
the query is：
1.what is the sawtooth shape？its usage is what？
2.why design it sawtooth shape？
3.What is the top and bottom of the sawtooth shape？
that's all，thank you
