Semiconductor device with protective films and manufacturing method thereof

A semiconductor device comprising:

• a semiconductor substrate including a drain part and a source part, the drain part and the source part being formed by doping an impurity into the semiconductor substrate;
• a first dielectric layer formed in an area between the source part and the drain part, the first dielectric layer including a first portion and a second portion whose thickness is smaller than a thickness of the first portion;
• a gate electrode formed on the area and disposed on the semiconductor substrate and the first and second portions of the first dielectric layer;
• a second dielectric layer formed to cover the gate electrode and a surface of the semiconductor substrate;
• a metal layer formed on the second dielectric layer;
• a first pad being electrically connected to the source part;
• a second pad being electrically connected to the drain part;
• a first protective film including silicon nitride as a principal component and being formed on the second dielectric layer and formed to directly cover the metal layer;
• and
• a second protective film containing carbon and being formed to directly cover the first protective film,
• wherein the second protective film is any of a phospho-silicate glass (PSG) film containing carbon, a boron phospho-silicate Glass (BPSG) film containing carbon, and an undoped silicon glass (USG) film containing carbon.