Unicode does not specify an encoding method, and the most common encoding method (UTF-8) isn't two-bytes per character: each character will be encoded as either 1, 2, 3, or 4 bytes. The next most common (UTF-16), will encode characters as either 2 or 4 bytes.

And, while we're talking about it, "extended ASCII" is kind of a generic term. It only specifies an 8-bit encoding where characters 0 through 127 are the same as ASCII (which is a 7-bit encoding), but it doesn't say anything about what characters 128 through 255 are. The most common are probably MS-Windows' "Code Page 1252" and ISO-8859-1, also known as "Latin-1", which encode mostly Western European characters there. Other "extended ASCII" sets exist for other sets of languages.