You can get back (almost 90% of it) after completing one year of continuous deposit. It takes 60-90 days for direct deposit in person's account.
Visit your local social security office and fill up a refund form (which is actually an application to main office in Geneva). Fyi the link/details of SVA office in Zurich city :http://www.svazurich.ch/home.cfm
Alternatively it can be transfered to your base country's social security scheme. Regards