Either diode pumping (for low currents - few mA) or dc-dc converter (switching regulator). Neither solution is particularly simple I'm afraid, unless you can buy one off the shelf.
Many DC-DC converters would fit the bill and are easy to find, depending on the other needs in your circuit. Im currently using the MAX731 in a couple of projects and it seems to work pretty damn reliably. The MAX631 does the same thing with less additional components, but didn't work as reliably as I'd like. The MAX751 might also work for you, and those are just a couple of options from one manufacturer.
You need to consider how much current the 2.2V source can supply, and how much current the 5V output needs to supply. Then the best method can be determined, if it is possible at all. You cannot obtain 5V at high current from 2.2V at low current, In other words you cannot create energy.
i found this one ic mc34063a that can act as a boost converter but then d minimum input voltage is 3 V..my project is to increase 2.2 V to 5 V...so anyone noes any other options...