If you think of the Newton-method using the Jacobian matrix, then there are lots of submissions on the internet. You can find many of them on the File Exchange too. However the simple Newton-method is not appropriate in most cases. Extend it with a line-search. If you have the Optimization Toolbox, use its fsolve function.
If you need to implement it on your own, then here is a resource: http://www.maths.lth.se/na/courses/FMN081/FMN081-06/lecture7.pdf.
