How to create COM in C# class lib ?

My company have many release programs written VB6.0 before.
Now, we want to add new functionalities in C#, and relpece old VB6
programs step by step.
Obviously, COM is a good way to do that.

In my program, I just to write a COM with C#, and invok it BV6.0
But I really can't understand why C# doesn't support "COM class"
template.( VB.Net provides this.)

I just want to know how to create COM in C# class lib ,and invoke it in VB6.

Thank you very much:-)

CYShao