Because of and because are used in different context. Because of is a prepositional phrase. However, Because is a conjunction.
Here are some examples: : I was unable to attend the meeting because of traffic jam. I was unable to attend the meeting because I was held up in a traffic jam.
Mary bought the leather bag because the design was very unique.
Mary bought the leather bag because of the unique design.
Raj could not come to college yesterday because of his fever.
Raj could not come to college yesterday because he had fever.
I am unable to drive fast because of heavy snow,
I am unable to drive fast because it is snowing heavily.